Method for manufacturing porous structure and method for forming pattern

ABSTRACT

A pattern forming material contains a block copolymer or graft copolymer and forms a structure having micro polymer phases, in which, with respect to at least two polymer chains among polymer chains constituting the block copolymer or graft copolymer, the ratio between N/(Nc−No) values of monomer units constituting respective polymer chains is 1.4 or more, where N represents total number of atoms in the monomer unit, Nc represents the number of carbon atoms in the monomer unit, No represents the number of oxygen atoms in the monomer unit.

This application is a Division of application Ser. No. 09/588,721 Filedon Jun. 7, 2000 now U.S. Pat. No. 6,565,763

BACKGROUND OF THE INVENTION

The present invention relates to a material that is capable of forming apattern of the order of nanometers in a self-organized manner on asubstrate, the pattern being utilized as a mask for forming ananopattern excellent in regularity. The present invention also relatesto a material that is capable of forming a bulk structure of the orderof nanometers in a self-organized manner, the structure being utilizedas it is as a nanostructure of high regularity, or utilized as atemplate for forming another nanostructure of high regularity. Thematerial of the present invention is applied for manufacturing amagnetic recording medium for hard disks having a recording density of10 Gbit/inch² or more, an electrochemical cell, a solar cell, aphotovoltaic device, a light emitting device, a display, a lightmodulating device, an organic FET device, a capacitor, a high-precisionfilter, etc.

Needs for a fine pattern or structure are increasingly desired, asimprovement in performance of electronic parts. In the electronic partssuch as LSI and liquid crystal display, for example, micro-fabricationtechniques are required. Many devices such as an electric cell and acapacitor are required small volume and large surface area. In future, ahigh-density three-dimensional packaging will be needed. Lithography isemployed in these processes, and thus the manufacturing cost becomeshigher as more micro-fabrications are needed.

On the other hand, there is a technical field where precision as high asin the case of the lithography is not needed, although a patterning ofthe order of nanometers is required. However, a simple patterning methodhas not known hitherto, there is no other choice to form a fine patternby lithography using an electronic beam or deep ultraviolet ray in sucha technical field. As mentioned above, in the lithography technique,operations are complicated and enormous investment is required as theprocessing dimension becomes smaller.

Under these circumstances, as a simple pattern forming methodalternative to the lithography technique, a method utilizing a structurehaving micro polymer phases formed in a self-developed manner from ablock copolymer.

For example, P. Mansky et al. have reported, in Appl. Phys. Lett., Vol.68, No. 18, p. 2586–2588, a method in that a sea-island typemicrophase-separated film made of a block copolymer of polystyrene andpolyisoprene is formed on a substrate, the polyisoprene is decomposed byozonation and removed to form a porous film, and the substrate is etchedusing the porous film as a mask, thereby forming a pattern, to which thestructure having micro polymer phases is transferred, on the substrate.In addition, M. Park et al. have reported, in Science, Vol. 276,1401–1406, a method in that a sea-island type microphase-separated filmmade of a block copolymer of polystyrene and polyisoprene is formed on asubstrate, the polyisoprene phase is doped with osmium oxide by a vaporphase reaction to improve etch resistance, and a pattern is formed usingthe polyisoprene phase selectively doped with osmium oxide as a mask.

Such a method using the microphase separation of the block copolymer issimple and inexpensive as compared with the lithography technique.However, the ozonation is complicated as well as needs relatively longreaction time, so that it is difficult to improve throughput. Also,since the osmium oxide has high level of toxicity, it is scarcely usedin general purpose from the viewpoint of safety.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide a pattern formingmaterial and a method for forming a pattern, which show high processthroughput and capable of forming very easily a planar pattern orthree-dimensional structure of the order of nanometers havingconsiderable regularity.

A still another object of the present invention is to provide a methodfor manufacturing easily a magnetic recording medium, a field emissiondisplay, a field emission cathode, a separator and electrode for anelectrochemical cell, a catalytic electrode for a fuel cell, a filter,etc., by making use of the aforementioned material.

A pattern forming material according to the present invention comprisesa block copolymer or graft copolymer having two polymer chains whoseratio between N/(Nc−No) values of respective monomer units is 1.4 ormore, where N represents total number of atoms in the monomer unit, Ncrepresents the number of carbon atoms in the monomer unit, No representsthe number of oxygen atoms in the monomer unit.

The block copolymer or graft copolymer satisfies the conditions istypically that having a polymer chain containing aromatic rings and anacrylic polymer chain.

A pattern forming material of the present invention contains a blockcopolymer or graft copolymer having a polysilane chain and acarbon-based organic polymer chain.

A method for forming a pattern of the present invention comprises stepsof: forming a molded product made of an above-mentioned pattern formingmaterial; forming a structure having micro polymer phases in the moldedproduct; and dry-etching the molded product to remove selectively apolymer phase from the structure having micro polymer phases, therebyforming a porous structure.

A method for forming a pattern of the present invention comprises stepsof: forming a film made of an above-mentioned pattern forming materialon a substrate; forming a structure having micro polymer phases in thefilm; selectively removing a polymer phase from the structure havingmicro polymer phases formed in the film by dry-etching; and etching thesubstrate using remaining another polymer phase as a mask, therebytransferring the structure having micro polymer phases to the substrate.

A method for forming a pattern of the present invention comprises stepsof: forming a pattern transfer film on a substrate; forming a film madeof a pattern forming material comprising a block copolymer or graftcopolymer having two polymer chains whose ratio between dry etch ratesis 1.3 or more on the pattern transfer film; forming a structure havingmicro polymer phases in the film; selectively removing a polymer phasefrom the structure having micro polymer phases formed in the film bydry-etching; etching the pattern transfer film using remaining anotherpolymer phase as a mask, thereby transferring the structure having micropolymer phases to the pattern transfer film; and etching the substrateusing the pattern transfer film as a mask to which the structure havingmicro polymer phases is transferred, thereby transferring the structurehaving micro polymer phases to the substrate.

Another pattern forming material of the present invention contains ablock copolymer or graft copolymer having a polymer chain whose mainchain is cut by irradiation with an energy beam and an indecomposablepolymer chain against irradiation with an energy beam.

An electron beam is typically used as the energy beam. The polymer chainwhose main chain is cut by irradiation with the energy beam is typicallyan acrylic chain substituted by a methyl group or halogen at α-positionor a polysilane chain.

A method for forming a pattern of the present invention comprises stepsof: forming a molded product made of an above-mentioned pattern formingmaterial; forming a structure having micro polymer phases in the moldedproduct; irradiating the molded product with an energy beam, therebycutting a main chain of a polymer phase in the structure having micropolymer phases; and selectively removing the polymer chain whose mainchain is cut by development or etching, thereby forming a porousstructure consisting of remaining another polymer phase.

A method for forming a pattern of the present invention comprises stepsof: forming a film made of an above-mentioned pattern forming materialon a substrate; forming a structure having micro polymer phases in thefilm; irradiating the film with an energy beam, thereby cutting the mainchain of a polymer phase in the structure having micro polymer phases;selectively removing the polymer chain whose main chain is cut from thestructure having micro polymer phases by etching; and etching thesubstrate using remaining another polymer phase as a mask, therebytransferring the structure having micro polymer phases to the substrate.

A method for forming a pattern of the present invention comprises stepsof: forming a pattern transfer film on a substrate; forming a film madeof an above-mentioned pattern forming material on the pattern transferfilm; forming a structure having micro polymer phases in the film;irradiating the film with an energy beam, thereby cutting the main chainof a polymer phase in the structure having micro polymer phases;selectively removing the polymer chain whose main chain is cut from thestructure having micro polymer phases by etching; etching the patterntransfer film using remaining another polymer phase as a mask, therebytransferring the pattern of the structure having micro polymer phases tothe pattern transfer film; and etching the substrate using the patterntransfer film to which the pattern of the structure having micro polymerphases is transferred as a mask, thereby transferring the structurehaving micro polymer phases to the substrate.

A still another pattern forming material of the present inventioncomprises a block copolymer or graft copolymer comprising: a polymerchain comprising a repeating unit represented by the following formula:

where R¹ and R² independently represent a substituted or unsubstitutedalkyl group, aryl group aralkyl group or alkoxyl group having 1 to 20carbon atoms, and a thermally decomposable polymer chain.

The thermally decomposable polymer chain is typically a polyethyleneoxide chain and a polypropylene oxide chain.

A method for forming a pattern of the present invention comprises stepsof: forming a film made of a pattern forming material comprising a blockcopolymer or graft copolymer having at least one thermally decomposablepolymer chain on a substrate; forming a structure having micro polymerphases in the film; removing the thermally decomposable polymer phasefrom the structure having micro polymer phases by heating to a thermaldecomposition temperature or more; etching the substrate using remaininganother polymer phase as a mask, thereby transferring the pattern of thestructure having micro polymer phases to the substrate.

A method for forming a pattern of the present invention comprises stepsof: forming a pattern transfer film on a substrate; forming a film madeof a pattern forming material comprising a block copolymer or graftcopolymer having at least one thermally decomposable polymer chain onthe pattern transfer film; forming a structure having micro polymerphases in the film; removing the thermally decomposable polymer phasefrom the structure having micro polymer phases by heating to a thermaldecomposition temperature or more; etching the pattern transfer filmusing remaining another polymer phase as a mask, thereby transferringthe pattern of the structure having micro polymer phases to the patterntransfer film; etching the substrate using the pattern transfer film asa mask, to which the pattern of the structure having micro polymerphases is transferred, thereby transferring the pattern of the structurehaving micro polymer phases to the substrate.

A method for forming a pattern of the present invention comprises stepsof: forming a molded product made of a pattern forming materialcomprising a block copolymer or graft copolymer having at least onethermally decomposable polymer chain; forming a structure having micropolymer phases in the molded product; removing the thermallydecomposable polymer phase by heating to a thermal decompositiontemperature or more, thereby forming a porous structure consisting ofremaining another polymer phase; and filling pores of the porousstructure with an inorganic material.

An electrochemical cell of the present invention comprises a pair ofelectrodes and a separator interposed between the electrodes andimpregnated with an electrolyte, wherein the separator is constituted bya porous structure formed by selectively removing a polymer phase from ablock copolymer or graft copolymer having a structure having micropolymer phases.

An electrochemical cell of the present invention comprises a pair ofelectrodes and an electrolyte layer interposed between the electrodes,wherein at least a part of the electrodes is constituted by a porousstructure formed by selectively removing a polymer phase from a blockcopolymer or graft copolymer having a structure having micro polymerphases. The porous structure typically made of carbon.

A hollow fiber filter of the present invention is made of a porousstructure formed by selectively removing a polymer phase from a blockcopolymer or graft copolymer having a structure having micro polymerphases.

A method for manufacturing a porous carbon structure of the presentinvention comprises steps of: mixing a precursor of thermosetting resin,a surfactant, water and oil, thereby preparing a microemulsion in whichcolloidal particles containing the precursor of thermosetting resin aredispersed; curing the precursor of thermosetting resin unevenlydistributed in the colloidal particles; removing the surfactant, waterand oil from the colloidal particles, thereby providing porousstructures of cured thermosetting resin; firing to carbonize the porousstructures.

A still another method for forming a pattern of the present inventioncomprises steps of: applying a blend of a polymer including a metalparticle and a block copolymer or graft copolymer to a substrate to forma film; forming a structure having micro polymer phases in the film andsegregating the metal particles covered with the polymer in a centralportion of a polymer phase or at an interface between the polymer phasesin the block copolymer or the graft copolymer; selectively or entirelyremoving the polymer phases by etching in which the metal particles aresegregated, thereby leaving the metal particles.

The method is suitably applicable to magnetic recording medium bydepositing a magnetic material on the remaining metal particles. Also,the method is suitable applicable to manufacture of a field emission bydepositing a conductor or semiconductor on the remained metal particlesto form emitters.

A method for manufacturing a capacitor of the present inventioncomprises steps of: forming a film made of a blend of a polymerincluding a metal particle and a block copolymer or graft copolymer;allowing the film to form a lamella structure having micro polymerphases and segregating the metal particles covered with the polymer in acentral portion of each polymer phase in the lamella structure; andaggregating the metal particles to form a metal layer in the centralportion of each polymer phase in the lamella structure.

A method for manufacturing a catalytic layer of a fuel cell of thepresent invention comprises steps of: forming a film made of a blend ofa block copolymer or graft copolymer including a metal particle and ablock copolymer or graft copolymer; forming a structure having micropolymer phases in the film and segregating the metal particles coveredwith the polymer at an interface between the polymer phases forming thestructure having micro polymer phases; and selectively removing apolymer phase in the structure having micro polymer phases, therebyleaving the metal particles on a surface of remaining another polymerphase.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIGS. 1A and 1B are atomic force micrographs (AFM) showing examples ofstructures having micro polymer phases of the block copolymers accordingto the present invention;

FIGS. 2A to 2D are diagrammatic views showing examples of structureshaving micro polymer phases of the block copolymers according to thepresent invention;

FIG. 3 is a graph showing the relationship between N/(Nc−No) value anddry etch rate of various polymers;

FIGS. 4A to 4C are cross-sectional views showing a method ofmanufacturing the magnetic recording medium of the present invention;

FIG. 5 is a cross-sectional view of an electrochemical cell according tothe present invention;

FIG. 6 is a cross-sectional view of another electrochemical cellaccording to the present invention;

FIG. 7 is a cross-sectional view of a direct methanol fuel cellaccording to the present invention;

FIGS. 8A to 8C are schematic views showing a method of manufacturing thecapacitor according to the present invention;

FIG. 9 is a cross-sectional view of a field emission display accordingto the present invention;

FIG. 10 is a cross-sectional view of another field emission displayaccording to the present invention;

FIG. 11 is an SEM micrograph of a carbon structure manufactured in thepresent invention;

FIG. 12 is an SEM micrograph of a carbon structure manufactured in thepresent invention; and

FIG. 13 is a perspective view showing a catalytic layer of a fuel cellaccording to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention will be described in more detail.

The principle of the present invention is that a film or a bulk-moldedproduct of a block copolymer or graft copolymer is formed, whichcopolymer is allowed microphase-separation, and then a polymer phase isselectively removed, thereby forming a porous film or porous structurehaving a pattern of the order of nanometers. The resultant porous filmcan be used for a mask for etching an underlayer to transfer thepattern. Also, the porous structure can be used as it is for variousapplications as well as can be used for a template for forming anotherporous structure. In the present invention, a difference in dry etchrates, decomposition properties against an energy beam or thermaldecomposition properties between two polymer phases is used in order toremove selectively a polymer phase from a structure having micro polymerphases. Since it is not necessary to use a lithography technique, highthroughput and reduced cost can be obtained.

First, the block copolymer and graft copolymer will be described. Theblock copolymer means a linear copolymer in which homopolymer chains arebonded together in a form of blocks. A typical example of the blockcopolymer is an A-B type block copolymer in which an A polymer chainhaving a repeating unit A and a B polymer chain having a repeating unitB are connected each other and having a structure of: -(AA—AA)-(BB—BB)-.It is possible to employ a block copolymer in which three of more kindsof polymer chains are bonded together. In the case of a triblockcopolymer, any of A-B-A type, B-A-B type and A-B-C type can be employed.A star type block copolymer in which one or more kinds of polymer chainsextend radialy from a central portion can be employed. A block copolymerof (A-B)n type or (A-B-A)n type having four or more blocks can beemployed. The graft copolymer has a structure comprising a polymer mainchain and another pendent polymer chains as side chains. In the graftcopolymer, plural kinds of polymers may be pendant as side chains. Also,a combination of a block copolymer and a graft copolymer comprising ablock copolymer, such as A-B type, A-B-A type and B-A-B type, andpendent polymer chains C can be employed.

The block copolymer is preferable compared to the graft copolymerbecause a polymer having a narrow molecular weight distribution can beeasily obtained and its composition ratio is also easily controlled.Note that, in the following description, the block copolymer will bemainly described, though the description concerning the block copolymeris applicable as it is to the graft copolymer.

The block copolymer and graft copolymer can be synthesized by variouspolymerization methods. The most preferable method is a livingpolymerization method. In the living anion polymerization or livingcation polymerization methods, the polymerization of a monomer isinitiated with a polymerization initiator capable of generating an anionor an cation, and then another monomer is successively added thereto,thus a block copolymer can be synthesized. A monomer having a doublebond such as vinyl compound or butadiene, a cyclic ether monomer such asethylene oxide, or a cyclic oligosiloxane monomer can be used as amonomer. It is also possible to use a living radical polymerizationmethod. According to the living polymerization method, the molecularweight and copolymer ratio can be precisely controlled, thus making itpossible to synthesize a block copolymer having a narrow molecularweight distribution. In the case where the living polymerization isemployed, it is preferable to dry sufficiently a solvent with adesiccant such as metal sodium and to prevent oxygen from mixing theretousing a method of freeze drying or bubbling of an inert gas. Thepolymerization reaction is preferably carried out under flow of an inertgas and under a pressurized condition of preferably two atm or more. Thepressurized condition is preferred because contamination of water andoxygen from outside the reaction vessel can be prevented effectively aswell as reaction process can be performed in relatively low cost.

A block copolymer and graft copolymer can also be synthesized by areaction between macromers such as telechelic polymers or bypolymerizing a different type of monomer from a macromer terminal as apolymerization initiation point. By making use of a reactive processingmethod, a block copolymer and graft copolymer can also be synthesized insitu by advancing the above reaction in the process of forming astructure having micro polymer phases. For example, an A polymer, inwhich reactive terminal groups or side chain groups are introduced, anda B monomer are mixed, and then the monomer is polymerized by a methodsuch as heating, light irradiation and addition of a catalyst in theprocess of forming a structure having micro polymer phases, thus a blockor graft copolymer comprising a polymer A and polymer B can besynthesized. In addition, a block or graft copolymer can be synthesizedin situ even by a method in which two or more kinds of telechelicpolymers each having a complementary bonding group at the ends or sidechains are blended.

It is preferable for a chemical bond linking the polymer chains witheach other to be a covalent bond from a viewpoint of bond strength, andparticularly preferable to be a carbon-carbon bond or a carbon-siliconbond.

Since special equipment and skill are required in the synthesis methodsof a block copolymer or a graft copolymer as compared with the generalradical polymerization, these methods have been mainly adopted in aresearch laboratory level, and therefore, the industrial applicationsthereof have been very limited in view of cost. However, in thetechnical fields such as an electronic industry where highly value-addedproducts are manufactured, a sufficient cost effectiveness can beobtained even if a block copolymer or a graft copolymer is employed.

The block copolymer and graft copolymer, unlike a random copolymer, canform a structure, i.e., a structure having micro polymer phases, inwhich an A phase consisting of aggregated A polymer chains are spatiallyseparated from a B phase consisting of aggregated B polymer chains. In aphase separation given by a general polymer, i.e., a macrophaseseparation, since two polymer chains can be completely separated to eachother, thus ultimately two phases are completely separated. Also, thescale of fluctuation generation is 1 μm or so, the size of a unit cellis 1 μm or more. On the contrary, the size of a unit cell in themicrophase separation given by a block copolymer of graft copolymer isnot made larger than the size of a molecular chain, which is in theorder of several nanometers or several tens nanometers. In addition, thestructure having micro polymer phases exhibits morphology in which fineunit cells are very regularly arrayed.

Various types of morphology of the structure having micro polymer phaseswill be described. FIGS. 1A and 1B are microphotographs with an atomicforce microscope (AMF) of a polystyrene (PS)-polymethacrylate (PMMA)block copolymer, which show plan views of structures having micropolymer phases. FIG. 1A is referred to as a dot structure or asea-island structure, whereas FIG. 1B is referred to as a worm-likestructure. FIGS. 2A to 2D show schematic views of the structures havingmicro polymer phases viewed stereoscopically. FIG. 2A is referred to asa sea-island structure in which another phases are sphericallydistributed in one phase. FIG. 2B is referred to as a cylindricalstructure in which another phases in a rod-like form are regularlydistributed in one phase. FIG. 2C is referred to as a bicontinuousstructure. FIG. 2D is referred to as a lamella structure in which Aphases and B phases are alternately and regularly laminated.

The structure having micro polymer phases of a block copolymer or graftcopolymer can be formed in the following manner. For example, a blockcopolymer or graft copolymer is dissolved in a suitable solvent toprepare a coating solution, which is applied to a substrate to form afilm. The film is annealed at a temperature above a glass transitiontemperature of the polymers, thus a favorable phase-separated structurecan be formed. It is also possible to use a method that a copolymer ismelted and annealed at a temperature in the range between above theglass transition temperature and below the phase transition temperatureto allow the copolymer to form a structure having micro polymer phases,and the structure having micro polymer phases is fixed at roomtemperature. A structure having micro polymer phases can also be formedby slowly casting a solution of a copolymer. A structure having micropolymer phases can also be formed by a method that a copolymer is meltedand molded into a desired shape by a hot press molding, an injectionmolding and a transfer molding, etc., followed by annealing.

According to the Flory-Huggings theory, it is required for the phaseseparation between an A polymer and B polymer that the free energy ΔG ofmixing must be positive. If the A polymer and B polymer are hard to beblended and the repulsive force between two polymers is intense, a phaseseparation easily occurs. In addition, the microphase separation easilyoccurs as a degree of polymerization of the block copolymer becomeslarge, and therefore, there is a lower limit in the molecular weight.However, polymers of respective phases forming the phase-separatedstructure are not necessarily incompatible with each other. As long asthe precursor polymers of these polymers are incompatible with eachother, the structure having micro polymer phases can be formed. After aphase-separated structure is formed by use of the precursor polymers,the precursor polymers can be reacted by heating, light irradiation oraddition of a catalyst to be converted into desired polymers. When thereaction conditions are suitably selected at that time, thephase-separated structure formed by the precursor polymers is notdestroyed.

The phase separation is most liable to occur when the composition ratioof an A polymer and B polymer is 50:50. This means that a structurehaving micro polymer phases that is formed most easily is a lamellastructure. On the contrary, there may be a case where, even by raisingthe content of one polymer, it is difficult to form a sea-islandstructure containing small islands consisting of the other polymer.Therefore, the molecular weight of the block copolymer may be animportant factor in order to obtain a desired structure having micropolymer phases.

However, it is very difficult to polymerize a block copolymer withprecisely controlling the molecular weight. Therefore, it may bepossible to adjust the composition ratio by measuring the molecularweight of the synthesized block copolymer and blending a homopolymer soas to give a desired composition ratio. The addition amount of thehomopolymer is set to 100 parts by weight or less, preferably 50 partsby weight or less, and more preferably 10 parts by weight or less to 100parts by weight of the block copolymer. If the addition amount of thehomopolymer is excessive, there is a possibility to disrupt thestructure having micro polymer phases.

In addition, if the difference between the solubilities of the twopolymer constituting the block copolymer is too large, there may beoccur a phase separation between the A-B block copolymer and the Ahomopolymer. In order to avoid the particular phase separation as muchas possible, it is preferable to lower the molecular weight of the Ahomopolymer. This is because the A homopolymer having a low molecularweight increases the negative value of the enthoropy term in theFlory-Huggins equation, making it easy for the A-B block copolymer andthe A homopolymer to be blended together. In addition, the fact that themolecular weight of the A homopolymer is lower than molecular weight ofthe A block in the block copolymer leads to thermodynamic stability.Taking the thermodynamic stability into consideration, it is preferablethat the molecular weight of the A homopolymer is lower than two thirdsof the molecular weight of the A block constituting the block copolymer.On the other hand, if the molecular weight of the A homopolymer islowered to less than 1,000, it may possibly be blended to the B block inthe block copolymer, which is not preferable. In addition, taking theglass transition temperature into consideration, the molecular weight ofthe A homopolymer is more preferably 3,000 or more.

When a thin film consisting of the pattern forming material of thepresent invention is formed, it is preferable to apply a homogeneoussolution. When the homogeneous solution is used, it is possible toprevent hysteresis during film formation from being remained. If thecoating solution is inhomogeneous as the case where micelles having arelatively large particle size are produced in the solution, it is madedifficult to form a regular pattern due to mixing of an irregularphase-separated structure or it takes a long time to form a regularpattern, which is not preferable.

The solvent for dissolving the block copolymer should desirably be agood solvent to two kinds of polymers constituting the block copolymer.The repulsive force between polymer chains is proportional to a squareof the difference in solubility parameter between two kinds of polymerchains. Consequently, when the good solvent to the two polymers isemployed, it makes the difference in solubility parameter between twokinds of polymer chains smaller and makes free energy of the systemsmaller, which leads to an advantageous condition for a phaseseparation.

When a thin film of a block copolymer is intended to form, it ispreferable to employ a solvent having a high boiling point of 150° C. ormore so as to make it possible to prepare a homogeneous solution. When abulk-molded product of a block copolymer is intended to form, it ispreferable to employ a solvent having a low boiling point such as THF,toluene and methylene chloride.

Examples of pattern forming materials used in the present invention willbe described hereinafter. First, a pattern forming material consistingof a block copolymer or graft copolymer comprising two or more polymerchains whose difference in dry etch rates is large will be described.The pattern forming material of the present invention comprises a blockcopolymer or graft copolymer comprising at least two polymer chainswhose ratio between N/(Nc−No) values of respective monomer units is 1.4or more, where N represents total number of atoms in the monomer unit,Nc represents the number of carbon atoms in the monomer unit, Norepresents the number of oxygen atoms in the monomer unit, and a blockcopolymer and a graft copolymer comprising a polysilane chain and acarbon-based organic polymer chain. The condition that the ratio betweenN/(Nc−No) values is 1.4 or more with respect to two polymer chains meansthe fact that the etching selectivity of each polymer chain constitutingthe structure having micro polymer phases is large. Namely, when thepattern forming material that meets the above condition is allowed toform a structure having micro polymer phases and then is subjected todry etching, a polymer phase is selectively etched and the other polymerphase is left remained.

The parameter of N/(Nc−No) will be described in detail below. In thisparameter, N is a total number of atoms per segment (which correspondsto monomer unit) of a polymer; Nc is the number of carbon atom; and Nois the number of oxygen atom. The parameter is an index indicating thedry etch resistance of a polymer, in that the etch rate by dry etchingis made higher (or the dry etch resistance is lowered) as the value ofthe parameter becomes larger. In other words, there is a followingrelationship between the etch rate V_(etch) and the aforementionedparameter.V_(etch)∝N/(Nc−No)

This tendency is scarcely dependent on the types of etching gas such asAr, O₂, CF₄, H₂, etc. (J. Electrochem. Soc., 130, 143(1983)). As for theetching gas, in addition to Ar, O₂, CF₄ and H₂ that are described in theabove publication, it is also possible to employ C₂F₆, CHF₃, CH₂F₂,CF₃Br, N₂, NF₃, Cl₂, CCl₄, HBr, SF₆, etc. Note that, the parameter hasnothing to do with the etching of an inorganic material such as silicon,glass and metal.

The specific value of the parameter can be calculated by referring tothe following chemical formula. Since the monomer unit of polystyrene(PS) is C₈H₈, the parameter is expressed as 16/(8−0)=2. Since themonomer unit of polyisoprene (PI) is C₅H₈, the parameter is expressed as13/(5−0)=2.6. Since the monomer unit of polymethacrylate (PMMA) isC₅O₂H₈, the parameter is expressed as 15/(5−2)=5. Therefore in the blockcopolymer of PS-PMMA, it is expected that the etch resistance of PS ishigher, and only PMMA is likely etched. For example, it has beenconfirmed that, when the block copolymer is subjected to a reactive ionetching (RIE) with flowing CF₄ in a flow rate of 30 sccm and setting thepressure to 0.01 Torr under the conditions of 150 W in progressive waveand 30 W in reflective wave, PMMA is etched at an etch rate that is4±0.3 times faster than PS.

FIG. 3 shows a relationship between the N/(Nc−No) value of each polymerand the etch rate thereof. The abbreviations employed in FIG. 3respectively represent the following polymers. SEL-N=(trade name, SomerKogyo Co., Ltd.), PMMA=polymethyl methacrylate, COP=glycidylmethacrylate-methyl acrylate copolymer, CP-3=methacrylate-t-butylmethacrylate copolymer, PB=polybenzyl methacrylate,FBM=polyhexafluorobutyl methacrylate, FPM=polyfluoropropyl methacrylate,PMIPK=polymethyl isopropenyl ketone, PS=polystyrene, CMS=chloromethlatedstyrene, PαMS=poly(α-methylstyrene), PVN=polyvinylnaphthalene,PVB=polyvinylbiphenyl, and CPB=cyclized polybutadiene. As shown in thefigure, it is found that the relationship of V_(etch)∝N/(Nc−No) iseffected.

In a polymer including an aromatic ring and having many double bonds,the value of the above parameter becomes smaller in general because theratio of carbon is relatively increased. As seen from theafore-mentioned parameter, the larger the number of carbon atom in thepolymer (the smaller the value of the parameter), the higher the dryetch resistance, and the larger the number of oxygen atom in the polymer(the larger the value of the parameter), the lower the dry etchresistance. This can be described qualitatively as follows. Namely,carbon is less reactive to radicals, and hence is chemically stable.Therefore, a polymer containing a large number of carbon atoms is hardlyreactive to various kinds of radicals, which leads to improve etchresistance. Whereas oxygen is highly reactive to radicals, so that apolymer having a large number of oxygen atoms is etched at a high etchrate, and thus has low etch resistance. Additionally, when oxygen isincluded in a polymer, oxygen radicals may be easily generated.Therefore, when a fluorine-based etching gas such as CF₄ is employed, Fradicals are multiplied due the effect of oxygen radicals and theradicals taking part in the etching are increased, leading to increasethe etch rate. An acrylic polymer has high oxygen content and a smallnumber of double bonds, which brings about increase in the value of theabove parameter, so that it can be easily etched.

Therefore, typical block copolymers having a large difference in dryetch rates comprise an aromatic ring-containing polymer chain and anacrylic polymer chain. An example of the aromatic ring-containingpolymer chain includes a polymer chain synthesized by polymerizing atleast one monomer selected from the group consisting of vinylnaphthalene, styrene and derivatives thereof. An example of the acrylicpolymer chain includes a polymer chain synthesized by polymerizing atleast one monomer selected from the group consisting of acrylic acid,methacrylic acid, crotonic acid and derivatives thereof.

As mentioned above, when the ratio of the N/(Nc−No) parameter betweenthe A polymer chain and the B polymer chain constituting the patternforming material is 1.4 or more, it is possible to obtain a clearpattern etching. When this ratio is 1.5 or more, preferably 2 or more,it is possible to ensure a large difference in etch rates between twokinds of polymer chain, thereby making it possible to enhance thestability in the processing. It is preferable in the actual dry etchingthat the etching selectivity between two kinds of polymer chains be 1,3or more, more preferably 2 or more, still more preferably 3 or more.When the ratio of the N/(Nc−No) parameter between the A polymer chainand the B polymer chain constituting the pattern forming material is 1.4or more, it is possible to obtain a satisfactory pattern by means ofetching without employing a polymer chain to which a metal element isdoped or a metal element is introduced. Since patterning can beperformed without employing a metal element, the material is very usefulfor manufacturing various electronic devices in which metal impuritiesbring about problems.

In order to enhance the etching selectivity in the case where O₂ gas isemployed as an etching gas, it is especially preferable to use asilicon-containing polymer chain as a polymer chain having higher etchresistance and a halogen-containing polymer chain as a polymer chainhaving lower etch resistance. As the silicon-containing polymer chain, asilicon-containing aromatic polymer chain such as poly(p-trimethylsilylstyrene) is preferred. As the halogen-containing polymer chain, ahalogen-containing acrylic polymer chain such as poly(chloroethylmethacrylate) is preferred.

Another pattern forming material consisting of a block copolymer orgraft copolymer comprising two or more kinds of polymer chains havinglarge difference in etch rates will be described. A pattern formingmaterial of the present invention comprises a block copolymer or graftcopolymer comprising a polysilane chain and a carbon-based organicpolymer chain.

The block copolymer having a polysilane chain can be synthesized bycopolymerization between a polystyrene-based macromer and dichlorosilaneas disclosed by S. Demoustier-Champagne et al (Journal of PolymerScience: Part A: Polymer Chemistry, Vol. 31, 2009–2014(1993)), or byliving polymerization between polysilane using masked disilene andmethacrylates as disclosed by Sakurai et al (Japan Chemical Society,76th Spring Meeting, Preprint I, Lecture No. 4B513). Since polysilane isa silicon-based polymer, which can be dry-etched easier than a generalcarbon-based polymer.

The polysilane chain employed in the pattern forming material of thepresent invention comprises any one of the repeating units representedby the following chemical formulas at least partly.

where R¹, R², R³ and R⁴ respectively represent a substituted orunsubstituted alkyl, aryl or aralkyl group having 1 to 20 carbon atoms.

The polysilane may be a homopolymer or a random copolymer, or may be ablock copolymer having a structure in which two kinds of polysilane arelinked together via an oxygen atom, a nitrogen atom, an aliphatic groupor an aromatic group. Examples of the polysilane includepoly(methylphenylsilane), poly(diphenylsilane),poly(methylchloromethylphenylsilane), poly(dihexylsilane),poly(propylmethylsilane), poly(dibutylsilane), and a random and blockcopolymer thereof.

Next, a pattern forming material utilizing difference in decompositionproperties by an energy beam between two or more polymer chainsconstituting a block copolymer or graft copolymer will be described. Thepattern forming material of the present invention comprises a blockcopolymer or graft copolymer comprising a polymer chain whose main chainis cut by irradiation with an energy beam and an indecomposable polymerchain against irradiation with an energy beam. The polymer chain whosemain chain has been cut by irradiation with the energy beam can beremoved by means of wet etching such as rinsing with a solvent or byevaporation by heat treatment. Thus, a fine pattern or a structureretaining a structure having micro polymer phases can be formed withouta dry etching process. There are some cases depending on the types ofelectronic materials where a dry etching process is not applicable or awet etching process is more preferable in view of manufacturing costeven if a dry etching process is applicable. Therefore, it is veryadvantageous not to use a dry etching process.

Since a block copolymer has two or more kinds of polymers linked througha chemical bond, the block copolymer is generally hard to be developedeven if one polymer chain represents high solubility to a developer.However, when a block copolymer of polystyrene (PS) and polymethylmethacrylate (PMMA), for example, is irradiated with an electron beam,the main chain of PMMA is cut, so that only the PMMA phase can bedissolved in the developer. The developer is not particularly restrictedas long as it can selectively dissolve out to remove the decomposedpolymer chain, and therefore it may be a water-based solvent or anorganic solvent. In the case of PMMA, methyl isobutyl ketone (MIBK),ethyl lactate, acetone, etc., can be employed. In order to adjust thesolubility of the polymer, other solvent such as isopropyl alcohol (IPA)may be added to the developer as well as a surfactant may be added.Ultrasonic cleaning may be performed during development. Since thepolymer chain after decomposition is lowered in molecular weight and canbe evaporated by heat treatment, it can be easily removed.

At least one polymer constituting a block copolymer or graft copolymeris cut in the main chain by irradiation with an energy beam such as anelectron beam, an X-ray, a γ-ray and a heavy particle beam. An electronbeam, an X-ray and a γ-ray are preferred since they can penetrate deepinto the molded product of the polymer and advantageous in view ofreducing processing cost because of relatively low cost in irradiationequipment. In particular, the electron beam and X-ray are morepreferable, and further the electron beam is most preferable because itbrings about high efficiency for decomposition of the polymer chain byits irradiation. As an electron beam source, various types of electronbeam accelerators such as Cockcroft-Walton type, Van de Graaff type,resonance transformer type, insulated-core transformer type, or lineartype, dynamitron type and radio frequency type can be employed.

The polymer chains decomposed by an energy beam include those having amethyl group at α-position such as polypropylene, polyisobutylene,poly(α-methylstyrene), polymethacrylic acid, polymethyl methacrylate,polymethacrylamide and polymethyl isopropenyl ketone. Also, a polymerchain whose α-position is substituted by a halogen atom exhibits higherdecomposition property in main chain. Further, methacrylate polymerswhose ester group is substituted by a fluorinated carbon or halogenatedcarbon such as polytrifluoromethyl methacrylate,polytrifluoromethyl-α-acrylate, polytrifluoroethyl methacrylate,polytrifluoroethyl-α-acrylate and polytrichloroethyl-α-acrylate are morepreferable because they exhibit high sensitivity to the energy beam. Inthe case where the energy beam is an X-ray, it is preferable that thepolymer contains a metal element because it brings about improvement indecomposition efficiency.

The main chain of another at least one polymer chain constituting theblock copolymer is indecomposable against irradiation with an energybeam. A polymer capable of cross-linking by irradiation with the energybeam is more preferred. As the polymer chain indecomposable againstirradiation with the energy beam, those having a hydrogen atom at theα-position of the polymer chain such as polyethylene, polystyrene,polyacrylic acid, polymethyl acrylate, polyacrylamide and polymethylvinyl ketone are preferred. In addition, a polymer chain having a doublebond such as 1,2-butadiene, which can be cross-linked by the energybeam, may be employed. Further, derivatives of polynorbornene,polycyclohexane, etc., may be employed.

The electron beam is particularly useful among energy beams for exposureof not only a thin film but also a bulk-molded product. Since anelectron beam exhibits high penetration efficiency to an organicmaterial, in the case, for example, where one of two phases ismethacrylic polymer whose main chain is decomposed by the electron beam,the polymer located inside the bulk is also decomposed. Therefore, whena three-dimensional phase-separated structure is formed by use of ablock copolymer or a graft copolymer, followed by irradiation with theelectron beam and development, regularly arrayed pores of the order ofnanometers can be easily formed with retaining the three-dimensionalstructure. Since such a structure that the regularly arrayed pores areformed has a very large specific surface area, it can be used for aseparator of a polymer battery or a capacitor and for a hollow fiber.

When a blend polymer of polystyrene (PS) and polymethyl methacrylate(PMMA) is irradiated with an ultraviolet ray, the side chain methylgroups of PMMA are eliminated and carboxylic acids are formed, bringingabout change in polarity, so that only one of the phases can be removedby utilizing difference in polarity. However, even when an ArF excimerlaser (193 nm) is employed as a light source and exposure is performedat an exposure dose of 1 J/cm², not more than about 1% of the side chainmethyl groups are eliminated. When a KrF excimer laser (248 nm), whichhas relatively weak energy, is employed as a light source, it isnecessary to perform exposure at an exposure dose of about 3.4 J/cm².Further, when an i-line (365 nm) or g-line (436 nm) of mercury brightlines is employed, almost no side chain methyl group is eliminated. Itis sufficient to set the exposure dose to about 10 mJ/cm² for exposureto a resist for an ordinary semiconductor, when the ArF or KrF excimerlaser is employed. Taking these facts into consideration, it will berecognized that the aforementioned exposure dose of the ultraviolet rayis very high, which brings about a significant burden to the apparatus.

In order to eliminate one polymer phase from the copolymer in which twoor more kinds of polymer chains are chemically bonded, it is preferableto cut the main chain of the polymer phase. However, high energy isrequired for the ultraviolet ray to cut the polymer main chain, whichfact brings a tendency to cause damage to the indecomposable polymerchain. Therefore, it is very difficult to eliminate one of the phases inthe copolymer by irradiation with the ultraviolet ray. In addition,since the ultraviolet ray is poor in penetration efficiency to thepolymer, it is not suitable for the purpose of making a bulk-moldedproduct porous. In particular, a block copolymer containing a structurecapable of absorbing the ultraviolet ray such as an aromatic ringimpairs the penetration efficiency. Further, since a polymer chaindecomposed by the ultraviolet ray in high sensitivity is hard to bepolymerized by living polymerization, it is difficult to control themolecular weight distribution or the molecular weight.

On the contrary, as described above, an electron beam, an X-ray or aγ-ray is very effective because of high penetration efficiency to amolded product and high selectivity in decomposition reaction as well ashigh decomposition efficiency and low cost. In particular, the electronbeam is most preferable because its irradiation can be performedconveniently and in low cost.

Although the exposure dose of the electron beam is not particularrestricted, it is preferable to set the exposure dose to 100 Gy–10 MGy,more preferably to 1 kGy–1 MGy, and particularly preferably to 10kGy–200 kGy. If the exposure dose is too small, the decomposable polymerchain cannot be sufficiently decomposed. If the exposure dose becomesexcessive, there is a possibility that the decomposed products of thedecomposable polymer chain may be three-dimensionally cross-linked toform a cured product as well as the indecomposable polymer chain may bedecomposed.

Although the accelerating voltage for the electron beam differsdepending on the thickness of the polymer molded product, it ispreferable to set the accelerating voltage to about 20 kV–2 MV for athin film having a thickness of 10 nm to several tens micrometers, andto about 500 kV–10 MV for a film having a thickness of 100 μm or moreand a bulk-molded product. The accelerating voltage may be raised if ametallic molded product is included in the polymer molded product andthe electron beam is shielded. Electron beams different in acceleratingvoltage may be applied. Further, the accelerating voltage may be variedduring irradiation with the electron beam.

Next, a pattern forming material consisting of a block copolymer orgraft copolymer comprising a thermally decomposable polymer chain willbe described. As for such a block copolymer or graft copolymer, it ispreferable to employ a copolymer synthesized from a thermallydecomposable polymer chain and a heat resistant polymer chain. Thedifference in thermal decomposition temperature between the thermallydecomposable polymer chain and the heat resistant polymer chain is 10°C. or more, preferably 50° C. or more, more preferably 100° C. or more.Here, the thermal decomposition temperature represents a temperaturewhere the weight of the polymer degreases by a half when the polymer isheated at 1 atm under an inert gas flow for 30 minutes.

It is preferable for the thermally decomposable polymer chain whose mainchain is decomposed by heating. On the other hand, it is preferable forthe heat resistant polymer chain to have a glass transition temperatureabove the thermal decomposition temperature of the thermallydecomposable polymer chain or to be constituted by a polymer that causesa cross-linking reaction or intramolecular cyclization reaction at atemperature below the thermal decomposition temperature of the thermallydecomposable polymer chain and converts into a heat-resistant structuresuch as a three-dimensional cross-linked structure or ladder structure.

Examples of the thermally decomposable polymer chain are a polyethersuch as polyethylene oxide and polypropylene oxide,poly(α-methylstyrene), an acrylic resin such as polyacrylate andpolymethacrylate, and polyphthalaldehide. Polyethylene oxide,polypropylene oxide, poly(α-methylstyrene) and an acrylic resin areparticularly preferable because they can be obtained by livingpolymerization as a polymer chain having a narrow molecular weightdistribution.

Examples of a carbon-based polymer chain among the heat resistantpolymer chain include polyacrylonitrile, a polyacrylonitrile derivativesuch as α-halogenated polyacrylonitrile, polyamic acid, polyimide, apolyaniline derivative, a polyparaphenylene derivative, apolycyclohexadiene derivative, polybutadiene, and polyisoprene. It ispreferable that the polymer chain is allowed to form a structure havingmicro polymer phases and then is made infusible by heating in air.Polyvinylidene chloride can also be employed as the heat resistantpolymer chain because it can be made infusible by an appropriate method.In order to enhance to make the polymer infusible, a radical generatoror a cross-linking agent may be added.

Among the heat resistant polymer chains, polyacrylonitrile and apolycyclohexadiene derivative are preferred because they can be formedinto a block copolymer having a narrow molecular weight distribution byanion polymerization or radical polymerization.

A block copolymer having a polyacrylonitrile chain can be synthesized bya method of, for example, T. Suzuki et al (Polymer Journal, Vol. 14, No.6, 431–438(1982)). In this method, a block copolymer is synthesized bypolymerizing acrylonitrile using a polyether, such as polyethylene oxidewhose terminal hydroxyl groups are anionized, as a reaction initiator. Agraft copolymer having a polyacrylonitrile chain can be synthesized byradical copolymerization between a macromer such as polyethylene oxideor polypropylene oxide having a methacrylate structure or a styrenestructure at ends and acrylonitrile. When the polyacrylonitrile chain issubjected to heat treatment at a temperature of 200° C. or more,preferably 400° C. or more, a pyridine type ladder-like conductivepolymer can be produced.

A block copolymer having a polycyclohexadiene derivative chain can besynthesized by living polymerization using a cyclohexadiene derivativemonomer and another monomer forming a thermally decomposable polymerchain. Further, the polycyclohexadiene derivative is converted intopolyparaphenylene by heating. The cyclohexadiene derivative monomer andthe polycyclohexadiene derivative are represented by the followingchemical formulas.

where R¹ and R² independently represent a substituted or unsubstitutedalkyl group, aryl group, aralkyl group or alkoxyl group having 1 to 20carbon atoms. Examples of R¹ and R² include a methyl group, ethyl group,isopropyl group, t-butyl group, phenyl group, methoxymethyl group andmethoxyl group.

As a polycyclohexadiene derivative, a polymer having a cyclic carbonatestructure such as that represented by the following chemical formula isalso suitable.

The polycyclohexadiene derivative linked at the 1- and 4-positions, asshown in the above chemical formula, is most preferable becausecross-linking occurs easily between neighboring polymer chains. However,a polycyclohexadiene derivative having a structure that linked at the 1-and 2-positions or a structure in which a portion that linked at the 1-and 2-positions and a portion that linked at the 1- and 2-positionscoexist can be employed. A combination of the heat resistant polymerconsisting of the polycyclohexadiene derivative polymer chain and thethermally decomposable polymer chain selected from polyethylene oxidechain and polypropylene oxide chain is preferred.

A polymer chain having sites at the side chain or the main chain that iscross-linked to form a heat resistant molecular structure can beemployed as a heat resistant polymer chain. For example, a polymerhaving a perylene skeleton in the side chains or the main chain can besuitable used. Also, a polymer chain having a siloxane cluster such asPOSS (Polyhedral oligomeric Silsesquioxane: polysiloxane T₈-cube) in theside chains or the main chain can be used. For example, a polymer chainsynthesized from the polysiloxane T₈ cube represented by the followingchemical formula is preferred.

where R represents H or a substituted or unsubstituted alkyl group, arylgroup or aralkyl group. Specific examples of R include a methyl group,an ethyl group, a butyl group, an isopropyl group and a phenyl group.

As a heat resistant polymer chain, polybutadiene or polyisoprenesynthesized by polymerizing a monomer having conjugated double bonds,followed by being three-dimensionally cross-linked at the side chain ormain chain with each other, may be used. 1,2-Polybutadien is mostpreferably used as an afore-mentioned cross-linkable polymer. Acopolymer comprising a polybutadiene chain may contain a little amountof 1,4-polybutadiene units besides the 1,2-polybutadien units. However,since the 1,4-polybutadiene unit is poor in cross-linking capability,the content of the unit is preferably 10% or less, more preferably 5% orless based on the total monomer units in the polybutadiene chain.

A block copolymer or graft copolymer having a polybutadiene chain orpolyisoprene chain as a cross-linkable polymer chain and a polyethyleneoxide chain or polypropylene oxide chain as a thermally decomposablepolymer chain is preferred.

These cross-linkable polymer chains are three-dimensionally cross-linkedwith each other by adding a radical generator or cross-linking agent.The cross-linkable polymer chain such as polybutadiene is hydrophobicand the polyethylene oxide chain is hydrophilic. Therefore, a radicalgenerator or cross-linking agent having relatively high hydrophobicityis preferred because it has a high affinity to the phase of thecross-linkable polymer chain.

Typical radical generator is organic peroxide. Examples of the organicperoxide include ketone peroxide such as methyl ethyl ketone peroxide,cyclohexanon peroxide, methyl cyclohexanon peroxide, methyl acetoacetateperoxide, and acetoacetate peroxide; peroxyketal such as1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane,1,1-bis(t-hexylperoxy) cyclohexane,1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,di-t-butylperoxy-2-methylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane,1,1-bis(t-butylperoxy)cyclododecane, 2,2-bis(t-butylperoxy)butane,n-butyl-4,4-bis(t-butylperoxy) valerate, and2,2-bis(4,4-di-t-butylperoxycyclohexyl) propane; hydroperxoide such asp-menthane hydroperxoide, diisopropylbenzene hydroperxoide,1,1,3,3-tetramethybutyl hydroperxoide, cumene hydroperxoide, t-hexylhydroperxoide, and t-butyl hydroperxoide; dialkyl peroxide such asα,α′-bis(t-butylperoxy)diisopropylbenzene, dicumyl peroxide,2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, t-butyl cumyl peroxide,di-t-butyl peroxide, and 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne;diacyl peroxide such as isobutyryl peroxide, 3,5,5-trimethylhexanoylperoxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide,succinic acid peroxide, m-toluoyl and benzoyl peroxide, and benzoylperoxide; peroxycarbonate such as di-n-propyl peroxydicarbonate,diisopropyl peroxydicarbonate, bis(4-t-butylcyclohexyl)peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, di-2-ethyhexylperoxydicarbonate, di-3-methoxybutyl peroxydicarbonate, anddi(3-methy-3-methoxybutyl) peroxydicarbonate; peroxy ester such asα,α′-bis(neodecanoylperoxy)diisopropylbenzene, cumyl peroxyneodecanoate,1,1,3,3-tetramethylbutyl peroxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, t-hexyl peroxyneodecanoate, t-butylperoxyneodecanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate,1,1,3,3-tetramethylbutyl peroxy-2-ethyhexanoate,2,5-dimethy-2,5-bis(2-ethylhexanoylperoxy)hexane,1-cyclohexyl-1-methyethyl peroxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-hexyl peroxyisopropylmonocarbonate, t-butylperoxymaleic acid, t-butyl peroxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, 2,5-dimethyl-2,5-(m-toluyl peroxy)hexane, t-butylperoxyisopropylmonocarbonate, t-butyl peroxy-2-etylhexyl monocarbonate,t-hexyl peroxybenzoate, 2,5-dimethyl-2,5-bis(benzoyl peroxy)hexane,t-butyl peroxyacetate, t-butyl peroxy-m-toluylbenzoate, t-butylperoxybenzoate, and bis(t-butyl peroxy)isophthalate; t-butylperoxyallylmonocarbonate, t-butyl trimethylsilyl peroxide,3,3′,4,4′-tetrakis(t-butyl peroxycarbonyl)benzophenone, and2,3-dimethyl-2,3-diphenylbutane. A polyfunctional radical generator suchas 2,2-bis(4,4-di-t-butyl peroxycyclohexyl)propane or3,3′,4,4′-tetra(t-butyl peroxycarbonyl)benzophenone is preferred becauseit also functions as a cross-linking agent. Also, a radical generatorsuch as azobisisobutylonitrile other than peroxide can be employed.

The addition amount of the radical generator is preferably 0.1 to 20 wt%, more preferably 1 to 5 wt % based on the cross-linkable polymerchain. If the amount of the radical generator is too small, density ofthe cross-linkage is decreased, whereas, if the amount of the radicalgenerator is too large, the cross-linked product may be porous or thestructure having micro polymer phases may be disordered.

In the case where the radical generator is added to a copolymercomprising a cross-linkable polymer chain, it is preferable that thecross-linking reaction is initiated after formation of the structurehaving micro polymer phases has sufficiently advanced. The formation ofthe structure having micro polymer phases occurs at a temperature abovethe glass transition temperature of each polymer chain in the copolymer.Therefore, it is preferable that the glass transition temperature of thepolymer chains is sufficiently lower than the radical generationtemperature of the radical generator.

From this point of view, preferred is a composition in which2,2-bis(4,4-di-t-butyl peroxycyclohexyl)propane or3,3′,4,4′-tetra(t-butyl peroxycarbonyl)benzophenone is added to a blockcopolymer comprising a 1,2-polybutadiene chain and a polyethylene oxidechain or polypropylene oxide chain by 1 to 5 wt % based on the1,2-polybutadiene chain. The glass transition temperature of1,2-polybutadiene is about 20° C., and the glass transition temperatureof the polyethylene oxide or polypropylene oxide is lower than 0° C.When each of 2,2-bis(4,4-di-t-butyl peroxycyclohexyl)propane and3,3′,4,4′-tetra(t-butyl peroxycarbonyl)benzophenone is heated at a rateof 4° C./min, the thermal decomposition temperatures of the radicalgenerators are 139° C. and 125° C., respectively.

When the above composition is heated to a temperature between roomtemperature and 50° C. to form a structure having micro polymer phasesand then is slowly heated to a thermal decomposition temperature of theradical generator, the cross-linkable polymer chains can be cross-linkedand cured. However, if the temperature is too high, there is apossibility that the composition reaches the order-disorder transitiontemperature before sufficient cross-linkage occurs and thus turns into ahomogeneous melt. In this case, 3,3′,4,4,′-tetra(t-butylperoxycarbonyl)-benzophenone is advantageous because it generatesradicals even when irradiated with an ultraviolet ray, which enablescross-linking at low temperature.

A block copolymer comprising a polybutadiene chain and anα-methylacrylic polymer chain can also be employed. An example is acomposition in which 2,2-bis(4,4-di-t-butyl peroxycyclohexyl)propane or3,3′,4,4′-tetra(t-butyl peroxycarbonyl)benzophenone is added to a blockcopolymer comprising a 1,2-polybutadiene chain and a polymethylmethacrylate chain by 1 to 5 wt % based on the 1,2-polybutadiene chain.The polymethyl methacrylate has a relatively high glass transitiontemperature of 105° C., but it is decomposed by irradiation with anelectron beam and is likely to evaporate by annealing at relatively lowtemperature. Namely, with respect to the polymethyl methacrylate, athermal decomposition promoting effect can be obtained.

In addition, when a thick film is formed by evaporating a solvent from asolution of a block copolymer comprising a polybutadiene chain and apolymethyl methacrylate chain, a preferable structure having micropolymer phases can be formed without annealing. In this case, when thesolvent is evaporated at a temperature sufficiently lower than thethermal decomposition temperature of the radical generator, the advanceof cross-linkage in the cross-linkable polymer chains may not disturbformation of the structure having micro polymer phases. This method canbe used advantageously where a nanostructure is manufactured by forminga thick porous film and filling the pores with metal. The same effectsimilar to that of the polymethyl methacrylate case be obtained even inthe case where poly(α-methylstyrene) is used.

In the polymethyl methacrylate or poly(α-methylstyrene), the glasstransition temperature can be adjusted by a substituent. For example,the glass transition temperatures of poly(n-propyl methacrylate) andpoly(n-butyl methacrylate) are 35° C. and 25° C., respectively.Therefore, a copolymer comprising such a polymer chain can be annealedat low temperature, making it possible to form a good structure havingmicro polymer phases. Poly(α-methylstyrene) substituted by a butyl groupat the 4-position also exhibits a low glass transition temperature.Polymethyl methacrylate substituted by an alkyl group having six or morecarbon atoms exhibits a lower glass transition temperature, but such apolymer likely to cause cross-linking reaction when irradiated with anelectron beam. Poly(n-propyl methacrylate), poly(n-butyl methacrylate)and poly(s-butyl methacrylate) are preferred because they have both alow glass transition temperature and a thermal decomposition promotingeffect by electron beam irradiation. Polymethacrylate substituted by abranched alkyl group such as a 2-ethylhexyl group exhibits the thermaldecomposition promoting effect by electron beam irradiation although ithas many carbon atoms, but its monomer is expensive. Taking easiness inavailability into consideration, poly(n-butyl methacrylate) andpoly(s-butyl methacrylate) are most preferred.

Polyisobutylene or polypropylene can also be used as a polymer chainhaving both a low glass transition temperature and a thermaldecomposition promoting effect by electron beam irradiation.

In the case where electron beam irradiation is performed to obtain thethermal decomposition promoting effect, 1,2-butadiene can becross-linked at the same time, the amount of the radical generator canbe decreased, and there is no need to add the radical generator in somecases. When the radical generator is not added, there is no need to usea copolymer having a low glass transition temperature, but there is atendency that the cross-linkage density is decreased. Therefore, it ispreferable, in this case, to add a cross-linking agent.

Examples of the cross-linking agent include bismaleimide, polyfunctionalacrylate, polyfunctional methacrylate, polyfunctional vinyl compound,and a silicon compound having a Si—H bond. In particular, bismaleimideis excellent in terms of heat resistance. Examples of bismaleimideinclude bis(4-maleimidophenyl)methane, bis(4-maleimidophenyl) ether,2,2′-bis[4-(paraaminophenoxy)phenyl]propane, and2,2′-bis[4-(paraaminophenoxy)phenyl]hexafluoropropane. The additionamount of the cross-linking agent is preferably 0.1 to 100 wt %, morepreferably 1 to 20 wt % based on the cross-linkable polymer chain. Ifthe addition amount is too small, the cross-linkage density isdecreased, whereas if the addition amount is too large, the structurehaving micro polymer phases is likely to be disturbed.

A cross-linked product of 1,2-polybutadiene is excellent in heatresistance, electric characteristics such as insulating property,moisture resistance and mechanical characteristics. Therefore, acomposition comprising a copolymer consisting of a 1,2-polybutadienechain and a polyethylene oxide, polypropylene oxide or polymethylmethacrylate chain and a radical generator is suitable for manufacturinga film for pattern formation or a porous structure. A porous materialconsisting of cross-linked polybutadiene is very useful because it canbe used for various filters.

A polysilane chain can be employed as a precursor of a heat-resistantpolymer chain. Chemical formulas, specific examples and synthesismethods for polysilanes are already described. The polysilane chain isphoto-oxidized by irradiation with an ultraviolet ray in air or anoxygen-containing atmosphere. As a result, reactive or cross-linkableradical terminals are generated by elimination of side chains andcutting of main chain and oxygen insertion produces siloxane bonds. Whenfired after the photo-oxidization, a cross-linking reaction mainlyinvolving the siloxane bond occurs, and the polysilane chain istransformed into a structure analogous to the SiO₂ structure. Also, whena polysilane chain or polycarbosilane chain is irradiated with anultraviolet ray under a nonoxygen or low-oxygen atmosphere and thenfired, the polymer chain is converted to silicone carbide (SiC). Theresultant SiO₂ or SiC exhibits high heat resistance.

An example of a preferable polysilane chain is one having an aromaticsubstituent and an alkyl group. Such polysilane has a repeating unitrepresented by the following chemical formula.

where R¹ represents a substituted or unsubstituted aromatic substituenthaving 6 to 20 carbon atoms wherein a phenyl group is most preferred,and R² represents a substituted or unsubstituted alkyl group having 1 to6 carbon atoms wherein a methyl group is most preferred.Poly(methylphenylsilane) is particularly preferred because it can beeasily cross-linked through the elimination of the phenyl group byirradiation with ultraviolet ray.

It is preferable to use a block copolymer consisting of a polysilanechain and a polyethylene oxide or polypropylene oxide chain. Such ablock copolymer is applied to a substrate by spin coating to form afilm, followed by forming a phase-separated structure, and then the filmis exposed to an ultraviolet ray, and heated if desired, to advancecross-linking reaction. Further, the film is heated to thermallydecompose to remove the thermally decomposable polymer chain. As aresult, a pattern of a product analogous to SiO₂ or SiC, to which aphase-separated structure is transformed, is formed. Using the patternas a mask, etching processing of the underlayer or plating can beperformed successfully.

An additive such as a sensitizer, radical generator and acid generator,for example, fullerene, 3,3′,4,4′-tetrakis(t-butylperoxycarbonyl)benzophenone and etc., can be added to the copolymerhaving a polysilane chain, if desired.

A polysiloxane chain can be used as a precursor of a heat resistantpolymer chain. The molecular weight distribution of the polysiloxanechain can be made small by living polymerization of cyclicoligosiloxane. When a polysiloxane chain having alkoxyl groups on theside chains is heated in a presence of an acid catalyst, it producessiloxane bonds accompanied by elimination of alkoxyl groups to bethree-dimensionally cross-linked, which brings about improvement in heatresistance and mechanical characteristics.

A polysilane chain and polysiloxane chain having hydroxyl groups oralkoxyl groups on the side chains are transformed into SiO₂ or SiO₂analogues by firing. Such polysilane and polysiloxane have a repeatingunit, for example, represented by the following chemical formulas.

where R¹ and R² independently represent a hydrogen atom, or asubstituted or unsubstituted alkyl group, aryl group or aralkyl grouphaving 1 to 20 carbon atoms. Specific examples are polysilane such aspoly(di-i-propoxysilane) and poly(di-t-butoxysilane), and polysiloxanesuch as poly(di-i-propoxysiloxane) and poly(di-t-butoxysiloxane).

When a block copolymer or graft copolymer having a polysilane chain orpolysiloxane chain and a thermally decomposable polymer chain such as apolyethylene oxide or polypropylene oxide chain is fired, a porousstructure consisting of an SiO₂ analogue material, to which aphase-separated structure is transformed, can be formed. Such a porousfilm functions well as a mask. Also, a porous structure can be appliedto various functional members such as a magnetic recording medium and anelectrode material by filling the pores with an inorganic material suchas metal.

Polyamic acid can be used as a heat resistant polymer chain. Whenpolyamic acid and an amino-terminated polymer are mixed, a carboxylgroup and an amino group forms a salt, thus a graft copolymer having apolyamic acid main chain and pendent amino-terminated polymers isformed. A Kapton precursor can be used as the polyamic acid. As theamino-terminated polymer, polyethylene oxide, polypropylene oxide orpolymethyl methacrylate having an aminopropoxyl group or dimethylaminopropoxyl group as one terminal group and a methoxyl group ordiphenylmethoxyl group as the other terminal group can be employed. Acopolymer consisting of polyamic acid and amino-terminated polypropyleneoxide is particularly preferable because it can be phase-separated well.In this case, varying the molecular weights of the polyamic acid andamino-terminated polymer, respectively, can control the size of domainsin the structure having micro polymer phases. Also, varying the mixingratio of the polyamic acid and amino-terminated polymer can easilychange morphology of the structure having micro polymer phases.

Examples of suitable combinations of a heat resistant polymer chain anda thermally decomposable polymer chain described above include: apolyacrylonitrile chain and a polyethylene oxide chain, apolyacrylonitrile chain and a polypropylene oxide chain, apolymethylphenylsilane chain and a polystyrene chain, apolymethylphenylsilane chain and a poly(α-methylstyrene) chain, apolymethylphenylsilane chain and a polymethyl methacrylate chain, apolymethylphenylsilane chain and a polyethylene oxide chain, and apolymethylphenylsilane chain and a polypropylene oxide chain.

A heat resistant material may be segregated on one polymer phase in ablock copolymer or graft copolymer consisting of a hydrophilic polymerchain and hydrophobic polymer chain. As the heat resistant material, aninorganic heat resistant material or a precursor thereof, orthermosetting resin can be employed. In this case, all of the polymerchains constituting the copolymer may be thermally decomposable. Forexample, in a block copolymer consisting of a polyethylene oxide chainand polypropylene oxide chain, both polymer chains are thermallydecomposable, but the polyethylene oxide chain is hydrophilic and thepolypropylene oxide chain is hydrophobic. When the inorganic heatresistant material or thermosetting resin is blended with the blockcopolymer, it is apt to be distributed unevenly on the hydrophilicpolyethylene oxide chain. When the blend is allowed to form a structurehaving micro polymer phases, followed by heating to thermally decomposeand evaporate the block copolymer, a porous pattern consisting of theinorganic heat resistant material or thermosetting resin, to which thestructure having micro polymer phases is transferred, can be formed.When the porous pattern is used as a mask, high etching selectivity canbe given. In addition, when a porous structure whose pores filled withmetal is used for a magnetic recording medium or an electrode, gooddurability can be given.

Examples of the inorganic heat resistant material or precursor thereofinclude a metal oxide gel, a metal alkoxide polymer, a metal oxideprecursor, a metal nitride precursor, metal fine particles, a metal saltand a metal complex. Examples of the metal include silicon, titanium,aluminum, zirconium, tungsten, and vanadium. The metal oxide gel can beobtained by hydrolysis of the metal alkoxide. Examples of the metalalkoxide include alkoxysilane such as tetramethoxysilane,tetraethoxysilane, tetraisopropoxysilane, tetraisopropoxyaluminum andtetraisopropoxytitanium, and alkylalkoxysilane such asbutyltriethoxysilane and propyltriethoxyaluminum. An example of themetal alkoxide polymer includes polydiethoxysiloxane. Examples of themetal oxide precursor or metal nitride precursor includepolysilsesquioxane, T-resin such as polyhedral oligomeric silsesquioxane(POSS), and polysilazane.

However, the metal oxide gel is poor in storage stability. In addition,if the cross-linking density of the metal oxide gel is too high,formation of a structure having micro polymer phases of a copolymer isdisturbed. Therefore, it is preferable that a solution in which a metaloxide gel precursor such as low-molecular weight metal alkoxide ororganic metal salt is mixed with a copolymer is applied to a substrateto form a film, followed by forming a structure having micro polymerphases, and then the precursor is transformed into a metal oxide gel bythe action of a catalyst such as an acid.

Further, it is preferable to use polysilsesquioxane, T-resin orpolysilazane. In particular, the T-resin does not disturb formation of astructure having micro polymer phases, since its curing rate bycross-linking can be controlled by a catalyst. After the structurehaving micro polymer phases is formed, T-resins can bethree-dimensionally cross-linked with each other and cured by thecatalyst. An example of T-resin is represented by the following chemicalformula.

where R¹ to R⁸ independently represent a hydrogen atom, a halogen atom,a hydroxyl group, a thiol group, an alkoxyl group, a silyloxyl group ora substituted or unsubstituted alkyl group, alkenyl group, alkynylgroup, aryl group or aralkyl group having a 1 to 20 carbon atoms.Specific examples of T-resin are: those having a hydrogen atom, methylgroup, hexyl group, vinyl group or dimethylsilyloxyl group as R¹ to R⁸,and those having cyclopentyl groups as R¹ to R⁷ and having a hydrogenatom, hydroxyl group, allyl group, 3-chloropropyl group or 4-vinylphenylgroup as R⁸.

Examples of polysilsesquioxane include polymethylsilsesquioxane,polymethylhydroxyl silsesquioxane, polyphenylsilsesquioxane,polyphenylmethylsilsesquioxane, polyphenylpropyl silsesquioxane,polyphenylvinylsilsesquioxane, polycyclohexylsilsesquioxane,polycyclopentyl silsesquioxane, polycyclohexylsilsesquioxane T₈-cube andpoly(2-chloroethyl)silsesquioxane.

In poly(2-bromoethyl)silsesquioxane, a cross-linking reaction proceedsat low temperature as well as the cross-linking can be performed byirradiation with an ultraviolet ray. Therefore, a polysiloxane-basedpolymer having a low glass transition temperature is used and astructure having micro polymer phases is formed, and then it can becured by UV irradiation. Polyhydroxylsilsesquioxane,polyphenylsilsesquioxane and poly-t-butoxysilsesquioxane can be used inthe similar manner as above.

Polyphenylsilsesquioxane is mixed with a copolymer, followed byformation of a structure having micro polymer phases, and then it can becross-linked and cured by the action of a curing catalyst. As the curingcatalyst, dibutyltin diacetate, zinc acetate, and zinc 2-ethylhexanoatecan be used. It is preferable to add the curing catalyst in the range of0.1 to 0.5 wt % based on the silsesquioxane. Silsesquioxane is mixedwith a copolymer, followed by formation of a structure having micropolymer phases, and then it can be cross-linked and cured byhydrochloric acid gas or a hydrochloric acid solution.

Examples of the thermosetting resin include: polyamic acid, epoxy resin,polyamide resin, polysulfide resin, urea-formaldehyde resin,phenol-formaldehyde resin, resorcinol-formaldehyde resin, furan resinsuch as furfuryl alcohol resin, melamine resin, aniline, resin,toluenesulfonic amide resin, isocyanate resin, alkyd resin, furfuralresin, polyurethane, resorcinol resin, polycarbodiimide, and a precursorpolymer of polyparaphenylenevinylene. The thermosetting resin ispreferred because it is excellent in storage stability as well as it canbe easily removed by ashing after it is used as a mask. In particular,polyamic acid, urea-formaldehyde resin, phenol-formaldehyde resin,resorcinol-formaldehyde resin, furan resin such as furfuryl alcoholresin and melamine resin are preferred, and polyamic acid is mostpreferable.

Examples of the hydrophilic polymer chain constituting a block copolymerinclude polyethylene oxide, poly(hydroxymethyl methacrylate),polyacrylic acid, polymethacrylic acid and carboxylate thereof,quarternized polyvinylpyridine, polyvinyl alcohol, andpoly(hydroxystyrene). In particular, polyethylene oxide,poly(hydroxymethyl methacrylate), polyacrylic acid and polymethacrylicacid are preferred.

Examples of the hydrophobic polymer chain constituting a block copolymerinclude polypropylene oxide, polystyrene, poly(α-methylstyrene),polymethacrylate, polybutadiene, polyisoprene, polysiloxane,fluorine-containing polymer. It is preferable that these polymer chainshave a low glass transition temperature and are thermally decomposableso as to be able to form a structure having micro polymer phases beforethe heat resistance material is cured. In particular, polypropyleneoxide, poly(α-methylstyrene) and polymethacrylate, which are thermallydecomposable at low temperature, and polysiloxane such aspolydimethylsiloxane, which has a low glass transition temperature arepreferred, and further polypropylene oxide and polydimethylsiloxane aremost preferable.

Examples of suitable combinations of polymer chains constituting a blockcopolymer or graft copolymer used together with a heat resistancematerial include: a polyethylene oxide chain and a polypropylene oxidechain, a polyethylene oxide chain and a polymethyl methacrylate chain, apolyethylene oxide chain and a poly(α-methylstyrene) chain, apolyethylene oxide chain and a polystyrene chain, a polyethylene oxidechain and a polyvinylpyridine chain, a poly(hydroxyethyl methacrylate)chain and a polypropylene oxide chain, a poly(hydroxyethyl methacrylate)chain and a poly(α-methylstyrene) chain, a poly(hydroxyethylmethacrylate) chain and a polystyrene chain, a polyacrylic acid chainand a polypropylene oxide chain, a polyacrylic acid chain and apolymethyl methacrylate chain, a polymethacrylic acid chain and apolymethyl methacrylate chain, a polyacrylic acid chain and apolyphenylmethylsiloxane chain, a polyethylene oxide chain and apolydimethylsiloxane chain, a polyethylene oxide chain and apolyphenylmethylsiloxane chain, and a polyethylene oxide chain and apolyvinylmethylsiloxane chain. Among these combinations, combinations ofthe polyethylene oxide chain and the polypropylene oxide chain, and thepolyethylene oxide chain and the polydimethylsiloxane chain arepreferred, and the combination of the polyethylene oxide chain and thepolydimethylsiloxane chain is most preferable. For example, acomposition in which thermosetting resin such as polyamic acid isblended with a block copolymer or graft copolymer of the polyethyleneoxide chain and the polydimethylsiloxane chain can be used well as acomposition for forming a pattern.

The mixing ratio between a heat resistance material and a blockcopolymer or graft copolymer is not particularly restricted. The heatresistance material is preferably used in the range of 1 to 500 parts byweight, more preferably 5 to 100 parts by weight, still more preferably10 to 50 parts by weight relative to 100 parts by weight of blockcopolymer or graft copolymer. If the mixing amount of the heatresistance material is too small, the composition cannot functionsufficiently as a mask. If the mixing amount of the heat resistancematerial is too large, the microphase-separation structure is disturbedand a good pattern cannot be formed.

A solvent used for preparing a solution of a mixture of a copolymer anda heat resistant material or precursor thereof should desirably be agood solvent to both the copolymer and the heat resistant material orprecursor thereof. In particular, it is preferable to use a goodsolvent, at the same time, to any of polymer chains constituting thecopolymer. If a solvent extremely poor in solubility to a particularpolymer chain is used, micelles are apt to be formed in the solution. Inthis case, on the occasion of forming a structure having micro polymerphases in a form of a thin film such as a mask for patterning or atemplate film for a magnetic film for a magnetic recording medium, thehysteresis of the micelle structure formed in the solution is leftremained, which makes it difficult to form a good pattern of thestructure having micro polymer phases.

In order to form a desired structure having micro polymer phases from ablock copolymer or graft copolymer, it is preferable to adjust thecomposition ratio between the two kinds of polymer chains, as describedabove. In the case of an A-B diblock copolymer, the morphology of thestructure having micro polymer phases varies depending on thecomposition ratio between the A polymer and the B polymer, asschematically described below. Where the ratio of a minority phase isvery small, the minority phase is aggregated to form spherical domainsinto a sea-island structure. When the composition ratio of two phasesbecomes 7:3, the minority phase forms columnar domains into cylindricalstructure. When the composition ratio of two phases becomes about 1:1,both phases form sheet-like domains that are alternately laminated intoa lamella structure.

Here, for the A-B diblock copolymer, the phase diagram leans toward theside of a polymer phase having a larger surface energy, i.e., having alarger value of solubility parameter. This means that the compositionwhere a domain structure such as a lamella, cylinder or sea-islandstructure is formed is slightly deviated depending on the combination oftwo kinds of polymer chains. Specifically, where the solubilityparameters of two kinds of polymers constituting a block copolymerdiffer from each other by about 1 cal^(0.5)/cm^(1.5), an optimumcomposition is shifted by about 5% toward the side of the polymer havinga larger solubility parameter relative to the afore-mentionedcomposition. Further, when a block copolymer is brought into contactwith a substrate, a polymer exhibiting a smaller surface energydifference tends to be segregated on the substrate side. For example, inthe case of PS-PMMA type block copolymer, PMMA tends to be precipitatedon the side of the substrate. On the contrary, in the case of PS-PB(polybutadiene) type block copolymer, PS tends to be precipitated on theside of the substrate.

In the case where a thin film of sea-island structure is to be formed,the composition ratio should desirably be set in the vicinity of thetransition point between the sea-island structure and the worm-likestructure. In this case, although an optimum composition ratio of theblock copolymer cannot be determined in a general way because aninteraction acts between the polymer and the substrate, the optimumcomposition ratio can be estimated in some measure. Namely, where theminority phase is a phase exhibiting smaller surface energy differencerelative to the substrate, the minority phase tends to be segregated onthe side of the substrate, and therefore it is necessary to set thecomposition of the minority phase larger. For example, since PMMA tendsto be segregated on the surface of the substrate in the case of PS-PMMA,it is necessary to set the ratio of PMMA in the copolymer in which PMMAconstitutes the minority phase than the ration of PS in the copolymer inwhich PS constitutes the minority phase. In addition, the sizedistribution of the spheres or cylinders becomes different due to thedifference in surface tension between the two kinds of polymers. Forthat reason too, the optimum composition ratio for forming aphase-separated structure differs between a block copolymer that an Apolymer constitutes the minority phase and a block copolymer that a Bpolymer constitutes the minority phase. For example, assuming that anoptimum composition ratio that the A polymer having an affinity to asubstrate forms dots on the substrate is A:B=20:80, there is a casewhere an optimum composition ratio that the B polymer forms dots on thesurface becomes A:B=85:15. This is because, as a polymer tends to beadsorbed on the substrate, an extra volume of polymer is required in thebulk.

It is preferable to set the volume fraction of the two polymer phasesconstituting a block copolymer as follows. For example, where thesea-island structure is to be formed, the volume fraction of one phaseis set to the range of 5 to 40%, preferably 10 to 35%, more preferably15 to 30%. The density of islands governs the lower limit of the volumefraction, while the range where the sea-island structure can bemaintained governs the upper limit. If the volume fraction exceeds theupper limit, another structure such as a cylindrical structure otherthan the sea-island structure is formed. Note that, where a thin filmhaving a thickness of about several tens nanometers is to be formed, theinfluence of the interface becomes significant, the above optimum valueshould be made smaller by 2 to 5%. In order to adjust the volumefraction of the two phases, the copolymerization ratio of the blockcopolymer may be controlled; alternatively the molecular volume of thepolymer chain may be controlled. The control the molecular volume can beachieved by various methods. For example, in the process of quaterize apolyvinyl pyridine chain, the molar volume of an alkyl group or acounter anion may be changed. Alternatively, a substance exhibits a highaffinity to a specific phase may be mixed so as to adjust the volumeratio of the phase. In this case, a homopolymer of a constituent polymerchain of the block copolymer may be employed as the substance to bemixed.

In order to form a good three-dimensional bicontinuous structure, it isrequired to be incompatible with each other between an A polymer chainand a B polymer chain; an A polymer chain and a precursor of B polymerchain; a precursor of A polymer chain and a B polymer chain; or aprecursor of A polymer chain and a precursor of B polymer chain. Where aprecursor is employed, the phase-separated structure is formed, and thenthe precursor is subjected to a chemical reaction under a temperaturecondition lower than the glass transition temperature of the copolymerto transform into a desired polymer chain. In this case, the molecularweight of each block should preferably be 3,000 or more. In order toadjust the composition ratio, a small amount of homopolymer may beadded, if desired, to a solution of the block copolymer having twopolymer chains incompatible with each other.

Various additives may be added to a solution of a block copolymer. Asfor the additive, it is preferable to use one having a specifically highaffinity to one of the polymer chains to be phase-separated to eachother. In this case, the additive can be easily segregated on thepolymer phase having a high affinity in the process of formation of thephase-separated structure. As a result, a phase containing the additivecan be improved in etch resistance. In particular, when the additive issegregated on a heat resistant phase, more excellent patterning can beperformed.

As for the additives, there may be used a metal salt of Cr, V, Nb, Ti,Al, Mo, Li, Lu, Rh, Pb, Pt, Au, Ru, etc., and an organic metal compound.A metal element produced by reducing such additives can be utilized as anucleus for a magnetic film of a magnetic recording medium of anelectrode material for an electrochemical cell. Examples of suchadditives include lithium 2,4-pentanedionate, lithiumtetramethylpentanedionate, ruthenium 2,4-pentanedionate, magnesium2,4-pentanedionate, magnesium hexafluoropentanedionate, magnesiumtrifuoropentanedionate, manganese(II) 2,4-pentanedionate, molybdenum(V)ethoxide, molybdenum(VI) oxide bis(2,4-pentanedionate), neodymium6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3.5-octanedionate, neodymiumhexafluoropentanedionate, neodymium(III) 2,4-pentanedionate, nickel(II)2,4-pentanedionate, niobium(V) n-butoxide, niobium(V) n-ethoxide,palladium hexafluoropentanedionate, palladium 2,4-pentanedionate,platinum hexafluoropentanedionate, platinum 2,4-pentanedionate, rhodiumtrifuoropentanedionate, ruthenium(III) 2,4-pentanedionate,tetrabutylammonium hexacholoroplatinate(IV), tetrabromoaurate(III)cetylpyridinium salt.

As an additive, metal fine particles having a size of several nanometersto 50 nm or less, which are surface-treated so as to enhance an affinityspecifically to one polymer phase, can be employed. Japanese Laid-openPatent Publication No. 10-251,548 discloses a method of coating metalparticles with a polymer. Japanese Laid-open Patent Publication No.11-60,891 discloses a method of coating metal particles with a polymer.For example, metal particles coated with an A homopolymer are segregatedon the A polymer chain in an A-B block copolymer, whereas metalparticles coated with a B homopolymer are segregated on the B polymerchain in an A-B block copolymer. In this case, the metal particles aresegregated on a polymer phase exhibiting a high affinity in the polymerchains constituting the A-B block copolymer. Further, metal particlescoated with an A-B block copolymer are segregated at the interfacebetween the A polymer chain and B polymer chain. By using such methods,the same type of metal element can be segregated freely on an arbitrarypolymer chain.

An additive may be chemically bonded to the side chain or main chain ofthe block copolymer, instead of merely mixing with the block copolymer.In this case, by modifying only a specific polymer with a functionalmolecular structure, it becomes easily possible to segregate theadditive on a specific phase. The additive may be introduced into apolymer chain by a method that a structure capable of easily bonding tothe additive is introduced into the main chain or side chain of aspecific polymer, and then a vapor or solution of the additive isbrought into contact with the polymer before or after the formation ofthe phase-separated structure. For example, when chelate structures areintroduced into a polymer chain, the polymer chain can be selectivelydoped with metal ions in a high concentration. The chelate structure maybe introduced into the main chain of a copolymer, or introduced into theester moiety of polyacrylate as a substituent group. When anion-exchange resin structure having an ionic group such as a pyridiniumsalt structure is introduced into a copolymer, the polymer chain can beeffectively doped with a metal ion by counter ion exchange.

The addition of a plasticizer to the pattern-forming material ispreferable as it enables to form a structure having micro polymer phasesby short time annealing. Although the addition amount of the plasticizeris not particularly restricted, the amount is set to 1 to 70 wt %,preferably 1 to 20 wt %, more preferably 2 to 10 wt % based on a blockcopolymer or a graft copolymer. If the amount of the plasticizer is toosmall, the effect of accelerating the formation of structure havingmicro polymer phases cannot be obtained sufficient, whereas if thecontent of plasticizer is excessive, the regularity of the structurehaving micro polymer phases may be disturbed.

Examples of the plasticizer include an aromatic ester and fatty acidester. Specific examples of the ester are a phthalate-based plasticizersuch as dimethyl phthalate, dibuthyl phthalate, di-2-ethylhexylphthalate, dioctyl phthalate and diisononyl phthalate; a trimelliticacid-based plasticizer such as octyl trimellitate; a pyromelliticacid-based plasticizer such as octyl pyromellitate; and a adipicacid-based plasticizer such as dibutoxyethyl adipate, dimethoxyethyladipate, dibutyldiglycol adipate and dialkyleneglycol adipate.

A polymerizable low-molecular weight compound can be added as aplasticizer. For example, the polymerizable low-molecular weightcompound such as bismaleimide is added to a block copolymer or graftcopolymer having a polymer chain having a relatively high glasstransition temperature, such as a polyimide chain or a polyamic acidchain that is the precursor of the former. The polymerizablelow-molecular weight compound serves as the plasticizer that enhancesfluidity of the polymer chain and promotes formation of thephase-separated structure in heating process. In addition, since thepolymerizable low-molecular weight compound is finally polymerized andcured to fix the structure having micro polymer phases, which makes itpossible to strengthen the porous structure.

Examples of bismaleimide include bis(4-maleimidophenyl)methane,bis(4-maleimidophenyl) ether,2,2′-bis[4-(paraaminophenoxy)phenyl]propane, and2,2′-bis[4-(paraaminophenoxy)phenyl]hexafluoropropane. The additionamount of the bismaleimide is set to 1 to 70 wt %, preferably 1 to 20 wt%, and more preferably 2 to 10 wt %. If the addition amount is toosmall, the cross-linkage density is decreased, whereas if the additionamount is too large, the structure having micro polymer phases is likelyto be disturbed. In the case where reinforcement of the structure havingmicro polymer phases by the polymerized product of the bismaleimide isintended, it is preferable to increase the addition amount of thebismaleimide. Specifically, it is preferable to add the bismaleimide inthe range of 10 to 50 wt % based on a polymer chain to be plasticizedsuch as a polyamic acid chain.

Addition of a cross-linking agent or introduction of a cross-linkablegroup to copolymers enables the copolymers to be cross-linkedtree-dimensionally with each other after the formation of the structurehaving micro polymer phases. Such a cross-linkage can improve thermal ormechanical strength of the structure having micro polymer phases moreeffectively and can enhance stability thereof. Taking heat resistanceinto consideration, it is preferable the respective polymer chains areessentially incompatible. However, even if the structure having micropolymer phases is constituted by phases not incompatible, the heatresistance thereof can be improved by cross-linking the polymer chainsforming the phases with each other.

When a structure having micro polymer phases is formed from a blockcopolymer, it is general to anneal the copolymer above the glasstransition temperature (and below the thermal decompositiontemperature). However, if the annealing is performed under anoxygen-containing atmosphere, there is a possibility that the polymer isdegenerated or degraded by an oxidation reaction, which makes itimpossible to form a good structure having micro polymer phases, or thetreatment time is prolonged, or desired etching selectivity cannot beobtained. In order to prevent such degradation of the copolymer, it ispreferable to perform the annealing under an oxygen-free condition andpreferably at a dark place where photo-degradation is hard to occur.However, the annealing under the oxygen-free condition requires strictcontrol of the atmosphere, which is likely to bring about increase inmanufacturing cost. Consequently, it is preferable to add an antioxidantor a light stabilizer to a block copolymer or graft copolymer. Althoughthe antioxidant or light stabilizer is not particularly limited, it ispreferable to employ a radical scavenger capable of trapping radicalspecies generated through an oxidation reaction or photo-degradationreaction.

Specifically, it is possible to employ a phenol-based antioxidant suchas 3,5-tert-butyl-4-hydroxytoluene; a phosphorus-based antioxidant; asulfur-based antioxidant such as a sulfide derivative; a hindered aminelight stabilizer (HALS) represented by a piperidine-based compound suchas bis-(2,2,6,6-tetramethylpiperidinyl-4) sebacate; or a metalcomplex-based light stabilizer such as copper and nickel.

Although the mixing amount of the antioxidant or light stabilizer is notparticularly limited, the amount is set to 0.01 to 10 wt %, preferably0.05 to 1 wt %, and more preferably 0.1 to 0.5 wt %. If the mixingamount is too small, antioxidant effect or light stabilizing effectbecomes insufficient. If the mixing amount is excessive, there is apossibility to disturb the phase-separated structure of the copolymer.

The antioxidant or light stabilizer may disturb smooth thermaldecomposition of a heat decomposable polymer chain on one hand.Therefore, it is preferable to employ those that can be evaporated ordecomposed at a temperature not lower than the heat decompositiontemperature of the heat decomposable polymer chain as the antioxidant orlight stabilizer. In addition, in the case where heat-resistant polymerchain is made infusible by heating in air so as to improve heatresistance, the presence of such an antioxidant should better beavoided. In this case, it is preferable for the antioxidant not to beevaporated at a temperature at which a structure having micro polymerphases is formed but to be evaporated or decomposed at a temperature atwhich the polymer chain is made infusible. Therefore, it is preferableto employ a compound such as 3,5-di-tert-butyl-4-hydroxytoluene that hasa low-molecular weight and is easily evaporated.

A method for forming a pattern according to the present invention willbe described in more detail hereinafter.

The method for forming a pattern of the present invention comprisessteps of: forming a film made of a pattern forming material on asubstrate; forming a structure having micro polymer phases in the film;removing one polymer phase selectively from the structure having micropolymer phases formed in the film; and etching the substrate with usingthe remaining another polymer phase to transfer the pattern of thestructure having micro polymer phases to the substrate.

This method can be applied to manufacturing of a fineparticles-dispersed type magnetic recording medium and a field emissiondisplay. Since the positions of elements in the pattern may not berequired so precise in these applications, this method is veryeffective.

First, a film made of a pattern forming material is formed on asubstrate by spin coating or dip coating. Annealing is performed, ifdesired, at a temperature above the glass transition temperature of thepattern forming material. The thickness of the film is preferably set toa thickness similar to or slightly larger than the size of the domainsin the structure having micro polymer phases to be formed. The size ofthe domain means a diameter of the islands in the case of sea-islandstructure, and a diameter of the cylinders in the case of cylindricalstructure. Specifically, the film thickness is preferably set to 0.5 to2.5 times, and more preferably 0.8 to 1.5 times relative to the domainsize.

In the case where employed as the pattern forming material is a blockcopolymer comprising two polymer chains whose ratio between N/(Nc−No)values of respective monomer units is 1.4 or more, where N representstotal number of atoms in the monomer unit, Nc represents the number ofcarbon atoms in the monomer unit, No represents the number of oxygenatoms in the monomer unit, or a block copolymer comprising a polysilanechain and a carbon-based organic polymer chain, the film is dry-etchedto remove selectively one phase from the structure having micro polymerphases. For example, in a block copolymer comprising a polymer chaincontaining an aromatic ring and an acrylic polymer chain, the acrylicpolymer phase is selectively dry-etched. Further, in a block copolymercomprising a polysilane chain and a carbon-based organic polymer chain,the acrylic polymer phase is selectively dry-etched.

In the case where employed as the pattern forming material is a blockcopolymer comprising a polymer chain whose main chain is cut byirradiation with an energy beam and an indecomposable polymer chainagainst irradiation with an energy beam, the film is irradiated with anenergy beam so as to cut the main chain of one polymer phase, and thenthe polymer phase is evaporated by heating or the polymer phase iswet-etched, thereby removing selectively the polymer phase. For example,when PS-PMMA having micro polymer phases is irradiated with an electronbeam and then developed with a developer, a PMMA phase is selectivelyremoved.

In the case where employed, as the pattern forming material is a blockcopolymer comprising a thermally decomposable polymer chain and a heatresistant polymer chain, heating the film above the thermaldecomposition film enables to evaporate the thermally decomposablepolymer phase constituting the structure having micro polymer phases andto remove selectively the polymer phase.

These methods make it possible to the film porous. The substrate isdry-etched or wet-etched using the resultant porous film as a mask,thereby transferring the pattern corresponding to the structure havingmicro polymer phases.

The method using an energy beam has an advantage that it can form a maskby wet etching without using a dry-etching process.

The thermal decomposition method makes it possible to form a mask byonly heat treatment. Further, since the surface of the substrate exposedat the holes of the mask is likely to be etched very easily, it canprovide a high contrast relative to the surface of the substrate coveredwith the mask. Since not only dry etching but also wet etching can beemployed for etching of the substrate, the range of selection of thesubstrate material that can be processed is made wide. When the wetetching is employed, process cost can be reduced.

In a conventional method for forming a mask in which a film having micropolymer phases is made porous by decomposing with ozone, it takes a longtime for decomposition with ozone. The method of the present inventioncan be carried out in shorter time compared to the conventional method.In particular, the thermal decomposition method makes it possible toform a good porous pattern in very short time, because it suffices tocarry out heat treatment.

An example of application of the aforementioned pattern forming methodto manufacturing of the magnetic recording medium will be described.This method comprises the following steps. (a) A nonmagnetic substrateis coated with a block copolymer comprising two kinds of polymer chainswhose etching resistivity differs with each other. (b) The blockcopolymer layer is allowed to form a sea-island structure having micropolymer phases. (c) A polymer phase poor in dry-etching resistivity isdry-etched, and further the nonmagnetic substrate is dry-etched usingthe remaining dry-etching resistant polymer phase as a mask. (d) Amagnetic layer is deposited in an etched region of the nonmagneticsubstrate. (e) The remaining polymer and the magnetic layer thereon islifted off. Hereinafter, each of the steps will be described in moredetail.

(a) As a block copolymer comprising two kinds of polymer chains whoseetching resistivity differs with each other, used is, for example, onecomprising dry-etching resistant PS and PMMA that is a polymer poor indry-etching resistivity in a ratio of about 8:2 or 2:8, where PMMAhaving a molecular weight of 50,000 or less and molecular weightdispersion of 1.1 or less. A solution in which the block copolymer isdissolved in, for example, a cellosolve-based solvent is applied to asubstrate by spin coating or the like.

(b) Annealing is performed to allow the block copolymer to form astructure having micro polymer phases, thereby forming a sea-islandstructure. An example of the sea-island structure includes a structurein which islands of PMMA having an average size of about 10 nm aredispersed in sea of PS. In the block copolymer, the etching selectivityby reactive ion etching (RIE) using CF₄ becomes to PS:PMMA=1:4 or more,and thus the etch rate of the islands is made larger.

(c) By performing RIE using CF₄, only the islands or sea of PMMA havinga higher etch rate in the block copolymer of the sea-island structureare etch-removed, and the sea or islands of PS are left remained.Subsequently, the non-magnetic substrate is etched using the remainingPS phase as a mask, thereby forming holes corresponding to portions ofthe islands or sea. Note that the (d) step may be preformed withoutetching the nonmagnetic substrate.

(d) A magnetic material is sputtered such that a magnetic layer isdeposited on the etched regions in the nonmagnetic substrate and on theremaining PS phase. Note that, an underlayer may be deposited prior todeposition of the magnetic layer.

(e) The remaining PS phase and the magnetic layer thereon are lifted offusing a solvent. Further, the remaining organic substance is finallyremoved by ashing or the like.

With using the above steps of (a) to (e), a magnetic layer can be formedin the nonmagnetic substrate or on the nonmagnetic substrate inaccordance with the pattern of the sea-island structure in the blockcopolymer layer. Since the method needs no mask-forming process, it isclearly understood that the method is inexpensive compared to the methodthat forms a mask by electron-beam writing. In addition, since aplurality of media can be annealed simultaneously, the method canmaintain high throughput.

An example of application of another pattern forming method according tothe present invention to manufacturing of the magnetic recording mediumwill be described with reference to FIGS. 4A to 4C. The method uses ablock copolymer and a polymer including metal fine particles as apattern forming material, which method makes it possible to arrange themetal fine particles at specific positions on a substrate without alift-off process.

First, a solution of a blend of an A-B block copolymer and an Ahomopolymer including metal fine particles is prepared, and the solutionis applied to the substrate 1 to form a film. As the A-B blockcopolymer, one having an acrylic polymer chain and aromatic-basedpolymer chain is employed, for example. In addition, as a polymercovering the metal fine particles, a polymer other than the A polymercan be employed as long as the polymer has a similar molecular structureto the A polymer and is incompatible with the B polymer. Annealing thefilm at a temperature above the glass transition temperature forms astructure having micro polymer phases in which the islands of the Apolymer phase 4 are present in the sea of the B polymer phase 3. In thisprocess, the metal fine particles covered with the A homopolymer aresegregated on the A polymer chain 4 constituting the structure havingmicro polymer phases, and thus the metal fine particles 5 are positionedat the central portions of the A polymer phases 4. In such a manner, astructure in which the metal particles are positioned at the centralportions in the island-like polymer phases can be formed with onlyperforming annealing of the film of pattern forming material (FIG. 4A).Incidentally, when metal fine particles covered with an A-B blockcopolymer instead of the A homopolymer are used, the metal fineparticles are segregated at the interface between the A polymer phaseand B polymer phase.

Then, with performing RIE, only the A polymer phases 4 (here, theacrylic polymer phases) constituting the structure having micro polymerphases are selectively etched. In this case, the metal fine particles 5are left remained in the holes 6 being formed without being etched (FIG.4B).

Further, when etching is continued using the remaining B polymer phase 3as a mask, the holes 7 are formed in the substrate 1, and the metal fineparticles 5 are left remained at the bottom of the holes 7 in thesubstrate 1. Thereafter, the remaining B polymer phase 3 is subjected toashing with oxygen plasma (FIG. 4C). By depositing magnetic materialusing the metal fine particles 5 present at the bottom of the holes 7 asseeds, a magnetic recording medium is formed.

The above method makes it possible to arrange the metal fine particlesat specific positions in the substrate without a lift-off process.Depositing a conductor or semiconductor on the metal fine particlesmakes it also possible to apply the method for forming an emitter of afield emission display.

Incidentally, it is preferable to select a pattern forming material tobe used appropriately. In order to form holes by etching a gateelectrode of a field emission array, in which holes emitter electrodesare formed, it is preferable to use such a pattern forming material asfollows. For example, the pattern forming material consists of a blockcopolymer or graft copolymer comprising an aromatic ring-containingpolymer chain and an acrylic polymer chain having a molecular weight of50,000 or more and molecular weight distribution (Mw/Mn) of 1.15 or lessin which the molecular weight ratio between the aromatic ring-containingpolymer chain and acrylic polymer chain ranges from 75:25 to 90:10.

In order to manufacture a magnetic recording medium of fineparticle-dispersed structure, it is preferable to use such a patternforming material as follows. For example, the pattern forming materialconsists of a block copolymer or graft copolymer comprising an aromaticring-containing polymer chain and an acrylic polymer chain having amolecular weight of the acrylic polymer chain of 100,000 or less andmolecular weight distribution (Mw/Mn) of 1.20 or less in which themolecular weight ratio between the aromatic ring-containing polymerchain and acrylic polymer chain ranges from 75:25 to 90:10.

In either pattern forming material, a minority phase (here, the acrylicpolymer phase) is removed by dry etching or by irradiation with anenergy beam. The size of the pattern in the structure having micropolymer phases is uniquely determined by the molecular weight of theminority polymer phase to be removed. Therefore, it is preferable to setthe molecular weight of the minority polymer to 100,000 or less. Whenthe polymer meets the conditions a dot pattern of a diameter rangingfrom 100 to 200 nm can be provided independently of the polymer type. Inthe case where a dot pattern of about 40 nm is to be formed, it ispreferable to set the molecular weight of the minority polymer to about10,000. If the molecular weight of the minority polymer becomes lowerthan 3,000, however, sufficient repulsive force between segments, whichis necessary for microphase-separation, cannot be provided, and thusthere is a possibility of disturbing distinct pattern formation.

A phase-separated structure of a pattern forming film can be oriented byan electric field. When an electric field of 1 to 10 V/μm is appliedduring formation of the structure having micro polymer phases in thepattern forming film by annealing, the structure having micro polymerphases is oriented. In the case of a cylindrical structure, for example,the cylinder phases are oriented along electric flux lines. When avoltage is applied to the pattern forming film along the directionparallel to the substrate, the cylinder phases are oriented along thedirection parallel to the substrate. Etching the substrate using theoriented pattern forming film as a mask makes it possible to form alinear pattern in the substrate. On the other hand, when a voltage isapplied to the pattern forming film with providing parallel plateelectrodes above and below the pattern forming film, the cylinder phasesare oriented along the thickness direction. With heat-treating thepattern forming film to make porous, a porous film having a high aspectratio in the depth direction. Etching the substrate using the orientedpattern forming film as a mask makes it possible to form holes having avery high aspect ratio in the substrate.

According to the present invention, it is also possible by utilizing apattern transfer technique to transfer a structure having micro polymerphases pattern of a pattern forming material to a pattern transfer filmand further to a substrate, thereby enabling to form holes having a highaspect ratio in the substrate. Note that, a lower pattern transfer filmmay be provided between the substrate and the pattern transfer film. Thepattern forming film, the pattern transfer film and the lower patterntransfer film will be described below.

1. Pattern Forming Film

As for a pattern-forming film, a block copolymer comprising two kinds ofpolymer chains whose dry etch rate ratio is 1.3 or more; a blockcopolymer having a polymer chain whose main chain is cut by irradiationwith an energy beam and an indecomposable polymer chain againstirradiation with an energy beam; or a block copolymer having a thermallydecomposable polymer chain and a heat resistant polymer chain, whichcontains one transformed form a precursor, can be employed. Such a blockcopolymer is applied by spin coating or dip coating to form a patternforming film. In this case, a pattern forming film in which cylinderphases are oriented by orientation with an electric field.

2. Pattern Transfer Films

The pattern transfer film is a layer to which a pattern formed in thepattern forming film is to be transferred, the film being provided underthe pattern forming film. After one polymer phase constituting thepattern forming film is selectively removed, the pattern transfer filmis subsequently etched. In order to remove one polymer phase in thepattern forming film, dry etching, electron-beam irradiation and wetetching, or thermal decomposition is employed in accordance with theabove pattern forming material.

The thickness and etch rate of the pattern transfer film is set so thatthe etching of the pattern transfer film can be accomplished before aphase having a higher etch resistance in the copolymer of the patternforming film is etched. Specifically, it is preferable that the patterntransfer film has a dry etch rate ratio of 0.1 or more, more preferably1 or more, still more preferably 2 or more compared to the polymer chainexhibiting lowest dry etch rate among the polymer chains constitutingthe block copolymer constituting the pattern-forming film. As for thepattern transfer film, a metal thin film formed of Au, Al, Cr, etc.;polysilane; or a polymer having N/(Nc−No) value of 3 or more that iseasily etched.

The polysilane as a pattern transfer film is not particularly restrictedas long as it contains a repeating unit represented by the followingchemical formulas.

where R¹ and R² represent a substituted or unsubstituted alkyl, aryl oraralkyl group having 1 to 20 carbon atoms, respectively.

Examples of the polysilane include poly(methylphenylsilane),poly(diphenylsilane) and poly(methylchloromethylphenylsilane). Further,the polysilane may be a homopolymer or a copolymer, or may be one havinga structure that two or more kinds of polysilane are bonded with eachother via an oxygen atom, a nitrogen atom, an aliphatic group or anaromatic group. An organosilicon polymer in which a polysilane and acarbon-based polymer are copolymerized can also be employed. Althoughthe molecular weight of the polysilane is not particular restricted, apreferable range of the molecular weight is Mw=2,000 to 1,000,000, morepreferably Mw=3,000 to 100,000. If the molecular weight is too small,the coating property and etch resistance of the polysilane will bedeteriorated. In addition, if the molecular weight is too small, thepolysilane film is dissolved when the pattern forming film is applied,thereby giving rise to mixing between the both films. On the other hand,if the molecular weight is too large, solubility of the polysilane to acoating solvent will be deteriorated.

Incidentally, since polysilane is liable to be oxidized and its etchingproperty is liable to be changed, it is preferable to add theaforementioned antioxidant or light stabilizer. Although the additionamount of the additives is not particularly restricted, it is preferableto be 0.01 to 10 wt %, more preferably 0.05 to 2 wt %. If the additionamount is too small, effect by addition cannot be obtained, on the otherhand, if the addition amount is too excessive, there is a possibilitythat the etching property of polysilane is deteriorated.

3. Lower Pattern Transfer Film

Provision of the lower pattern transfer film, although the lower patterntransfer film may not necessarily be provided, enables to obtain apattern having a high aspect ratio as well as to widen selection rangesof substrate materials to be processed. Since the lower pattern transferfilm is etched using the pattern transfer film as a mask, to which thestructure having micro polymer phases has been transferred, the etchingselectivity of the lower pattern transfer film relative to the patterntransfer film is preferably set to 2 or more, more preferably 5 or more,still more preferably 10 or more. In order to give high etchingselectivity, it is preferable to use an inorganic thin film made ofmetal or metal oxide as a pattern transfer film for a patter formingfilm made of an organic polymer, and to use an organic polymer film as alower pattern transfer film. In this case, etching the lower patterntransfer film with O₂ gas using the pattern transfer film as a maskenables to form very deep holes. Etching the substrate using these filmsas masks makes it possible to form deep holes having a high aspect ratioin the substrate. In order to give a high aspect ratio in the depthdirection, it is preferable to etch the lower pattern transfer film byanisotropy etching. Incidentally, when etching selectivity between thepattern transfer film and lower pattern transfer film is sufficientlyhigh, the pattern transfer film may be made thin, and thus the patterntransfer film may be etched by isotropy etching such as wet etching.

In the case where the lower pattern transfer film is used, it ispreferable to use, as the pattern transfer film, a metal such as Al, AuAg and Pt or a metal oxide such as silica, titanium oxide and tungstenoxide. In particular, aluminum is preferred because it has a gooddeposition property and can be etched by both etching processes of wetetching and dry etching. Although an organic polymer used for the lowerpattern transfer film is not particularly restricted, preferred is apolymer having high dry etch resistance against a freon type gas such asCF₄, for example, polystyrene or a derivative thereof such aspolyhydroxystyrene, polyvinylnaphthalene or a derivative thereof, andnovolak resin. The lower pattern transfer film may not necessarily beformed of a block polymer as well as may not necessarily be uniform inmolecular weight, so that it is possible to use an organic polymer thatcan be mass-produced industrially by means of radical polymerization orthe like and is relatively inexpensive.

A method for forming a pattern in which lower and upper pattern transferfilms and a pattern forming film are formed on a substrate and etchingprocesses are performed thrice will be described.

First, a film made of a polymer as described above is formed as a lowerpattern transfer film on a substrate by means of spin coating ordipping. The thickness of the lower pattern transfer film shoulddesirably be equal to or larger than the depth of holes to betransferred. A film formed of an inorganic material such as a metal orSiO is formed as an upper pattern transfer film on the lower patterntransfer film by means of vacuum evaporation or plating. The thicknessof the upper pattern transfer film should desirably be less than thethickness of a pattern forming film to be formed thereon. Any patternforming film as described above is formed on the upper pattern transferfilm. The thickness of the pattern forming film should desirably bealmost the same as the size of a structure to be formed. For example, inthe case where a sea-island structure comprising islands having a sizeof about 10 nm is to be obtained, the thickness of the film shouldpreferably be about 10 nm.

The dry etch rate of the upper pattern transfer film should preferablybe higher than that of the pattern forming film that is made porous.Specifically, it is preferably that the upper pattern transfer film isetched in a rate of at least 1.3 times, more preferably twice or morethe rate for the pattern forming film. However, in the case where apolymer film is provided as a lower pattern transfer film under theupper pattern transfer film, the above etch rate ratio may notnecessarily be met. Namely, after the upper pattern transfer film isetched, the lower pattern transfer film is etched with oxygen plasma. Onthis occasion, when the upper pattern transfer film has high resistanceagainst oxygen plasma, the lower pattern transfer film can be easilyetched with oxygen plasma. In this case, the dry etch rate of the upperpattern transfer film may be 0.1 or so compared to that of the patternforming film.

After these films are formed as mentioned above, annealing is performed,if desired, thus a structure having micro polymer phases is formed inthe pattern-forming film. RIE with a fluorine-based gas, electron-beamirradiation and wet etching, or thermal decomposition is performed,thereby removing one polymer phase selectively in the structure havingmicro polymer phases formed in the film and leaving another polymerphase. The upper pattern transfer film (for example, a metal) is etchedto transfer the structure having micro polymer phases (for example, asea-island structure) to the film. Then, RIE with oxygen plasma isperformed using the remaining upper pattern transfer film as a mask,thereby etching the lower pattern transfer film (for example, apolymer). Since oxygen RIE does not etch the upper pattern transfer filmformed of a metal, but etches only the lower pattern transfer filmformed of an organic polymer, it is possible to form a structure havinga very high aspect ratio. Simultaneously, the pattern forming filmformed of an organic copolymer is subjected to ashing. RIE with afluorine-based gas is performed again using the remaining lower patterntransfer film as a mask, thereby etching the substrate. As a result,holes of the order of nanometers and having a very high aspect ratio canbe formed in the substrate. Although wet etching can be employed inplace of RIE in the above processes, the shape of the pattern is likelyto be deformed during the pattern transfer process.

A method for manufacturing various porous structures using a patternforming material of the present invention will be described.

A method for manufacturing a porous structure of the present inventioncomprises the steps of: forming a molded product made of a patternforming material comprising a block copolymer or graft copolymer;forming a structure having micro polymer phases in the molded product;and dry-etching the molded product to remove selectively a polymer phasefrom the structure having micro polymer phases, thereby forming a porousstructure.

The structure having micro polymer phases formed in the bulk moldedproduct of a block copolymer or graft copolymer is preferred to be acontinuous phase structure such as a cylindrical structure, a lamellastructure and a bicontinuous structure, and particularly preferred isthe bicontinuous structure. The bicontinuous structure includesmorphology such as an OBDD structure, a Gyroid structure, a T-surfacestructure and a lamella catenbid structure.

In the case where used as the pattern forming material is a blockcopolymer comprising two polymer chains whose ratio between N/(Nc−No)values of respective monomer units is 1.4 or more (where N representstotal number of atoms in the monomer unit, Nc represents the number ofcarbon atoms in the monomer unit, No represents the number of oxygenatoms in the monomer unit), or a block copolymer comprising a polysilanechain and a carbon-based organic polymer chain, the film is dry-etchedto remove selectively one polymer phase from the structure having micropolymer phases.

In the case where used as the pattern forming material is a blockcopolymer comprising a polymer chain whose main chain is cut byirradiation with an energy beam and an indecomposable polymer chainagainst irradiation with an energy beam, the film is irradiated with anelectron beam to cut the main chain of one polymer phase constitutingthe structure having micro polymer phases, followed by wet-etching,thereby removing the polymer phase selectively.

In the case where used as the pattern forming material is a blockcopolymer comprising a thermally decomposable polymer chain and a heatresistant polymer chain, which contains one transformed form aprecursor, the film is heated to a temperature above the thermaldecomposition temperature to evaporate the thermally decomposablepolymer phase constituting the structure having micro polymer phases,thereby removing the polymer phase selectively.

Among these methods, the method of performing energy beam irradiationand wet etching and the thermal decomposition method are preferredbecause the steps are made simple, the cost is lowered, and a relativelythick porous structure can be manufactured.

For example, used is a block copolymer having an indecomposable polymerchain constitutes the porous structure and a polymer chain to be removedby energy beam irradiation and wet etching. As for the energy beam to beirradiated, an electron beam (β ray), X-ray and γ-ray are preferablebecause they have higher penetration property into a molded product. Inparticular, the electron beam is most preferred because it has highselectivity in decomposition reaction, has high decomposition efficiencyand can be applied at a low cost.

Examples of the indecomposable polymer chain constituting the porousstructure include polystyrene; polystyrene derivatives such aspolyhydrostyrene; novolak resin; polyimide; acrylonitrile-based resinsuch as acrylonitrile homopolymer and a copolymer of acrylonitrile andanother vinyl polymer; polyacrylic acid, and polyacrylate such aspolymethyl acrylate and polytrifluoroethyl-α-chloroacrylate; vinylidenefluoride-based resin such as vinylidene fluoride homopolymer and acopolymer of vinylidene fluoride and hexafluoropropylene; vinylchloride-based resin; vinylidene chloride-based resin; aromatic ketoneresin such as polyether ketone and polyether ether ketone; polysulfone;and polyether sulfone. In particular, acrylonitrile-based resin andvinylidene fluoride-based resin are preferred in view of durability.

Examples of a polymer chain that is cut in the main chain and removed byenergy beam irradiation include polyolefin such as polypropylene andpolyisobutylene; poly-α-methylstyrene; polymethacrylic acid andpolymethacrylate such as polymethyl methacrylate andpolytrichloroethylmethacrylate; polymethacrylamide; polyolefin sulfonesuch as polybutene-1-sulfone, polystyrenesulfone,poly-2-butylenesulfone; and polymethyl isopropenyl ketone. Inparticular, preferred are polyhexafluorobutyl methacrylate andpolytetrafluoropropyl methacrylate that are polymethacrylate in whichfluorine is introduced, and polytrifluoroethyl-α-chloroacrylate that ispolymethacrylate in which the α-methyl group is substituted by chlorine.

In the case where the method of applying electron-beam is employed, itis particularly preferable to use, as a polymer chain constitutes theporous structure, a polymer having double bonds such as1,2-polybutadiene in which cross-linking reaction can be advanced byelectron beam irradiation, derivatives of polynorbornen orpolycyclohexane, and vinylidene fluoride-based resins such as acopolymer of vinylidene fluoride and hexafluoropropylene.

As the block copolymer having a thermally decomposable polymer chain anda heat resistant polymer chain, various block copolymers that have beenalready described can be employed. Further, after the porous structuremade of a polymer is formed, the structure is fired and carbonized, andthus a porous carbon structure can also be manufactured.

The manufactured porous structure can be applied to various uses.Specific uses include a separator of an electrochemical cell, a filtersuch as a hollow fiber filter, ultra-fine fiber and porous fiber.

In another method of manufacturing a porous structure of the presentinvention, a porous structure is formed from a molded product of apattern forming material containing a block copolymer by such methods asdescribed above, and then the pores in the porous structure are filledwith an inorganic substance. This is a method for manufacturing astructure of the inorganic substance using the pores, which are formedby transferring the structure having micro polymer phases of the blockcopolymer or graft copolymer, as a template.

For example, a molded product is formed by casting or melting with usinga pattern forming material containing a block copolymer comprising athermally decomposable polymer chain and a heat resistant polymer chain.Next, annealing is performed, if desired, thus a structure having micropolymer phases is formed. Then, the structure is heated to a temperatureabove the thermal decomposition temperature of the thermallydecomposable polymer chain to remove selectively the thermallydecomposable polymer chain, thereby forming a porous structure retainingthe structure having micro polymer phases. The pores of the porousstructure are filled with, for example, a metal, an inorganic compoundsuch as a metal oxide and a carbon material such as diamond by platingor CVD. Thereafter, the heat resistant polymer phase is selectivelyremoved by O₂ ashing, if desired, and thus a structure of inorganicsubstance is formed. Further, transfer processes may be repeated usingthe resultant structure of inorganic substance as a template to formanother structure of organic substance or inorganic substance. A porousstructure consisting of a heat resistant polymer phase is particularlyexcellent because it is hard to be thermally deformed, and besides, itcan be easily removed by O₂ ashing or the like.

In this method, the pores of the porous structure are filled with aninorganic substance by plating or CVD. Therefore, it is preferable thatopenings are present on the surface of the porous structure andcontinuous pores are present in the porous structure. As a structurehaving micro polymer phases capable of forming pores as above, acylindrical structure, a bicontinuous structure or a lamella structureis preferred. In particular, the cylindrical structure and bicontinuousstructure are excellent because they can easily retain the shape of thepores in the porous structure. The OBDD structure and Gyroid structureincluded in the bicontinuous structure are particularly preferredbecause they are easily filled with a metal.

In the case where the porous structure is a thin film having a thicknessnearly equal to the domain size of the structure having micro polymerphases, a sea-island structure may be formed. When the porous structureof the sea-island structure is used as a template, a dot pattern of aninorganic substance can be formed. For example, a porous film exhibitinga sea-island structure is formed on a conductive substrate consistingof, for example, a metal. At that time, the conductive substrate isexposed to outside at the bottom of holes. When the substrate is notexposed to outside, the substrate is made exposed to outside by lightlyetching the porous film with oxygen plasma. Plating by passing anelectric current through the conductive substrate can form a dot-likemetal pattern.

Alternatively, a porous film exhibiting a sea-island structure is formedon a hydrophilic glass substrate to make the glass substrate exposed tooutside at the bottom of the holes. Then, electroless plating isperformed by adding a catalyst to deposit a metal on the bottom ofholes, thereby making it possible to a dot-like metal pattern.

In order to fill the porous structure with a metal, an inorganiccompound or carbon, used is a liquid phase process such as plating or avapor phase process such as CVD.

In the case of metal filling, electroplating or electroless plating isemployed. The electroplating is performed with connecting an electrodeto the porous structure. For example, a pattern forming film is formedon an electrode, and the film is made porous. The electrode is immersedin a plating bath, and then a current is passed through the electrode,thereby depositing a metal in the porous structure. In this case, it ispreferable to perform treatment to make the inner surface facing to theholes hydrophilic by plasma treatment, for example, so that the platingsolution can easily penetrate inside the holes in the porous structure.

After the porous structure is filled with a precursor of metal or metaloxide such as an organic metal compound, the porous structure may befired so as to be evaporated as well as the precursor may be convertedinto a metal or metal oxide. As the precursor of metal, an organic metalsalt, silsesquioxane, etc., can be employed. As a method for fillingwith these precursors, electrodeposition, spin coating, evaporation,sputtering, impregnation, etc., can be employed.

Also in the case of manufacturing a porous structure, a phase-separatedstructure of a molded product made of a pattern forming material may beoriented by an electric field in the same manner as described inrelation to the method for forming a planar pattern. For example, when afilm of a pattern forming material is formed on a substrate and then avoltage is applied to the film in the direction parallel to thesubstrate, cylinder phases are oriented in the direction parallel to thesubstrate. Thereafter, when the cylinder phases are removed by, forexample, dry etching or thermal decomposition, the surface of thesubstrate is made exposed. Deposition of a metal on the exposed portionsof the surface of the substrate by plating or CVD can form striped metalpattern, which can be used as fine metal wires.

For example, on an insulating wafer made of, for example, siliconnitride, two electrodes are formed with leaving a space of about 5 μm.The wafer is spin-coated with a PGMEA solution of PS-PMMA diblockcopolymer to form a thin film having a thickness of about 10 nm to 1 μm.Annealing is performed at 230° C. for 40 hours with applying a voltageof 10 V between the two electrodes. During the operation, microphaseseparation of the diblock copolymer is caused, and a cylindricalstructure, which is perpendicularly oriented to the electrodes, isformed. The PMMA phases in the structure having micro polymer phases areremoved by reactive ion etching or energy beam irradiation. As a result,a pattern of the order of nanometers perpendicular to the electrodes isformed. When the pattern as a template is filled with a metal byelectroplating or sputtering, ultrafine metal wires can be formed.

When parallel plate electrodes are provided above and below a patternforming film to apply a voltage, cylinder phases are oriented to thethickness direction. Removal of the cylinder phases can form a porousfilm in which narrow holes having a high aspect ratio are oriented inthe thickness direction. When one electrode is removed and the film isimmersed in a plating solution to perform electroplating by passing acurrent through the remaining electrode, a pinholder-like structure, inwhich fine metal wires having a diameter of 10 to 100 nm are oriented inthe direction perpendicular to the electrode, can be formed. It is alsopossible to use such a method that a metal such as palladium use as aplating nucleus is deposited on a substrate, a porous film is formed onthe metal using a similar procedure as above, and then holes are filledwith a metal by electroless plating. In this case, when the porous filmis made appropriately swelled using a solvent, it is possible todecrease the diameter of holes. When the porous film having narrowedholes is used as a template, a pin holder-like structure, in which veryfine metal wires having a diameter of several nanometers are oriented inthe direction perpendicular to the electrode, can be formed. Fine wiresof a metal oxide and various ceramic materials or the like can be formedin a similar method. This structure can be suitably employed as emittersin a field emission display (FED). In the application to the emitter, itis preferable to form the metal wires using gold, chromium, iridium orthe like, in that iridium is particularly preferable in view of heatresistance. In the case of forming emitters in FED, it is preferablethat the thickness of the porous film is larger than the length of themetal wires to be formed; specifically, the thickness is preferred to be1.5 times or more, more preferably 2 times or more the average length ofthe metal wires. This is because if a metal is deposited not only in theholes but also on the surface of the porous film, it is difficult toform emitters of a pin holder-like structure. The aspect ratio of theemitters (length/diameter of the metal wires) should preferably be notless than 10, more preferably not less than 50 to provide excellentfield emission characteristics. For example, when emitters having adiameter of 3 nm and an aspect ratio of 10 or more are to be formed, theporous film is preferred to have a thickness of 45 nm or more.

In the application to the emitters in FED, the porous film shouldpreferably be removed by ashing or the like because remaining porousfilm becomes a cause of gas generation. However, when a polymer chainconstituting a porous film is made of a material such aspolysilsesquioxane that can be converted into an inorganic material, itis preferable to leave the porous film because the film can retain thepin holder-like structure.

It is also possible to use a method that metal wires manufactured asdescribed above are once removed from the electrode and then they areadhered as emitters to another electrode, which is separately prepared.In this case, since emitters can be formed with only using an adhesionstep, the manufacturing process can be simplified. However, since themetal wires are not oriented in many cases, field emission efficiencytends to be lowered.

When employed is a block copolymer having a polymer chain whose mainchain is cut by irradiation with an energy beam and an indecomposablepolymer chain against irradiation with an energy beam, variouscombinations of polymer chains as described above may be applied.However, from the viewpoint of orientation characteristics and etchingcontrast, preferred is a diblock copolymer having a decomposable polymerchain selected from poly(meth)acrylate such as polymethyl methacrylate,polymethyl acrylate, polytrifluoromethyl-α-chloroacrylate andpolytrichloroethyl methacrylate and a indecomposable polymer chainselected from polystyrene, polyhydroxystyrene, polyvinylnaphthalene andderivatives thereof.

To form a highly oriented cylindrical structure, it is desirable to setthe molecular weight ratio between the decomposable polymer and theindecomposable polymer to the ranges of 75:25 to 67:34 and 34:67 to25:75. In the range of between 67:34 and 34:67, cylinders may possiblycoalesce with each other. If the composition is more weighted comparedto 75:25 or 25:75, it is difficult to give continuous cylindricalstructure.

Intervals in the pattern can be set to the range of about 10 nm to about1 μm, depending on the molecular weight of the block copolymer. A blockcopolymer having a molecular weight of about 10,000 is employed where apattern of a size of about 10 nm is to be formed, and a block copolymerhaving a molecular weight of about 100,000 for a pattern of a size ofabout 100 nm. If the molecular weight is lower than 3,000, a structurehaving micro polymer phases is hard to be formed, whereas, if themolecular weight exceeds 1,000,000, there is a possibility thatregularity of a structure having micro polymer phases is impaired.

Next, application of the porous structure of the present invention to anelectrochemical cell such as a lithium ion secondary battery or anelectrochromic device will be described. FIG. 5 shows a conceptualdiagram of an electrochemical cell. The electrochemical cell has astructure in which provided are the positive electrode 71 and thenegative electrode 72, each of which is provided with a collector, andthe separator 73 impregnated with an electrolyte and interposed betweenthe electrodes.

In the electrochemical cell of the present invention, used as theseparator 73, for example, is a porous structure formed by removing onepolymer phase selectively from a block copolymer having a structurehaving micro polymer phases. The separator can be manufactured by usinga pattern forming material comprising a block copolymer having, forexample, a polymer chain decomposable by irradiation with an energy beamand an indecomposable polymer chain, as described below. First, a sheetof a pattern forming material is formed, followed by allowing the sheetto form a structure having micro polymer phases. The sheet is irradiatedwith an energy beam to decompose the main chain of one polymer phase.Next, the sheet is placed between the negative electrode and thepositive electrode via a roll-to-roll process, and then they arehot-pressed. The laminate of pressed electrodes and separator is rinsedwith a solvent to remove the polymer phase whose main chain has beendecomposed, thereby making the separator sheet porous. Here, the polymerphase whose main chain has been decomposed may be evaporated and removedby reducing pressure or heating. After being sufficiently dried, thelaminate is immersed in a bath of an electrolytic solution containing asupporting electrolyte, etc., thereby allowing the laminate to beimpregnated with the electrolytic solution. Lead wires, etc., areconnected to the resultant laminate, followed by sealing the laminatewith an aluminum laminate film, for example, thus manufacturing anelectrochemical cell.

When an accelerating voltage for electron beam is sufficiently raised,the separator sheet is irradiated with an electron beam passed through acollector formed of a metal mesh and an active material for electrode.Therefore, the polymer main chain can also be decomposed by irradiationwith an electron beam after the separator and electrodes are pressed.This method is preferable because the possibility that thephase-separated structure by pressing is minimized.

It is preferable to mix a spacer consisting of metal oxide particles(such as silica particles) with the pattern forming composition so as tosecure a clearance between electrodes when two electrodes and aseparator are pressed. The size of the metal oxide particles shouldpreferably be set to about 20 to 90% relative to the clearance betweenthe electrodes.

In order to make it easy for a washing solution and electrolyte solutionto pass through the electrodes to the separator, the positive electrode71 and the negative electrode 72 should preferably be formed into anintricate structure such as aggregated particles or a porous structureas shown in FIG. 6. In this case, the separator 73 formed of a porousstructure is in a state of intruding in pores of these electrodes. Theelectrodes of intricate structure can be manufactured by a method thatan active material for electrode is mixed with a binder comprising apattern forming material, followed by being applied to the collector.Employment of such electrodes makes it possible to prevent contactresistance with an electrolyte from being increased, and at the sametime, to prevent liquid leakage.

The porous structure constituting the separator should preferably havean aggregated structure of domains having a radius of gyration of 50 μmor less in which unit cells having radius of gyration of 10 to 500 nmare periodically arranged. Such a separator has a good property ofretaining electrolyte solution and is hard to bring about liquid leakagebecause of pores having a size of the order of nanometers as well as isexcellent in ion conductivity because of less structural traps (such asdead-end pores). Particularly preferred is a porous structure havingcontinuous pores to which a bicontinuous phase-separated structure istransferred. Among bicontinuous structures, an OBDD structure and Gyroidstructure are particularly preferred because they exhibit high ionconductivity, which is attributed to the fact that ions are hard to betrapped in these structures, and are also excellent in film strength.The pore size is preferably set to 5 to 200 nm, more preferably 10 to100 nm, although it is not particularly limited. If the pore size is toosmall, ion conduction will be inhibited. If the pore size is too largeon the contrary, retention capacity for electrolyte solution will belowered.

The electrolyte solution to be impregnated into the separator may be onethat an inorganic salt or organic salt is dissolved in water or a polarsolvent, or may be a room-temperature molten-salt. In the case of alithium ion secondary battery, an electrolyte solution that a lithiumsalt is dissolved in a polar solvent or in room-temperature molten-saltis employed. As the lithium salt, employed is LiPF₆, LiBF₄, LiClO₄,LiSCN, Li₂B₁₀Cl₁₀, LiCF₃CO₂, lithium triflate, or the like. As the polarsolvent, employed is a carbonate-based solvent such as ethylenecarbonate, propylene carbonate and diethyl carbonate; a lactone-basedsolvent such as γ-butyrolactone; sulfolane-based solvent such assulfolane and 3-methylsufolane; and ether-based solvent such as1,2-dimethoxyethane and methyldiglyme. As the room temperaturemolten-salt, employed is an imidazolium salt such as1-methyl-3-ethylimidazolium triflate and a pyridinium salt such asN-butylpyridinium triflate.

As the negative electrode, employed is a copper mesh coated with amixture comprising an active material for negative electrode such asgraphite and hard carbon, conductive graphite and a binder polymer,preferably a pattern forming material. As the positive electrode,employed is an aluminum mesh coated with a mixture comprising an activematerial for positive electrode such as lithium cobaltate, conductivegraphite and a binder polymer, preferably a pattern forming material.

In an electrochemical cell of the present invention, electrodes mayconsist of a porous structure formed by selectively removing a polymerphase from a block copolymer having a structure having micro polymerphases.

Such a porous structure can be formed by, for example, a method that astructure having micro polymer phases is formed in a molded productconsisting of a block copolymer having a thermally decomposable polymerchain and a heat-resistant polymer chain and then the thermallydecomposable polymer is decomposed and evaporated to form pores, therebymaking the molded product porous. As the method for making the moldedproduct porous, it is possible to employ a method of decomposing andremoving a specific polymer phase by irradiation with an electron beamand a method of removing a specific polymer phase by dry etching.

It is particularly preferable to form a porous carbon electrode using acarbon precursor polymer as a heat-resistant polymer phase and firingthe heat-resistant polymer phase made porous. Examples of carbonprecursor polymer include polyacrylonitrile, polymethacrylonitrile,polyimide derivatives, polyaniline derivatives, polypyrrole derivatives,polythiophene derivatives, polyparaphenylenevinylene derivatives, andpolycyclohexadiene derivatives.

Annealing a molded product of a block copolymer having a carbonprecursor polymer and a thermally decomposable polymer is performed toform a structure having micro polymer phases. The thermally decomposablepolymer is decomposed to remove by heating, thereby forming a porousstructure consisting of the remaining carbon precursor polymer. Firingthe porous structure makes it possible to provide a porous carbonelectrode to which the structure having micro polymer phases istransferred. When the structure having micro polymer phases is acylindrical structure, lamella structure or bicontinuous structure, aporous carbon electrode containing continuous pores is given. Such aporous carbon electrode can be suitably used for a carbon negativeelectrode for a lithium ion secondary battery, an electrode for a fuelcell, an electrode for an electric double layer capacitor, etc. Inparticular, a porous carbon electrode that retains a bicontinuousstructure is excellent in interfacial area and morphology retention.Among bicontinuous structures, preferred is an OBDD structure or Gyroidstructure.

A porous structure, to which a structure having micro polymer phases istransferred, can be formed using a blend of a block copolymer and acarbon precursor, the block copolymer comprising a thermallydecomposable polymer chain and a polymer chain having high affinity withthe carbon precursor. It is preferable to applying an energy beam suchas an electron beam to cross-link the carbon precursor polymer chains.In this case, the structure having micro polymer phases is hard to becollapsed when the porous structure is fired. Alternatively, the carbonprecursor polymer chains may be oxidatively cross-linked by heattreatment in air.

The firing temperature is set to 500 to 1500° C. for the negativeelectrode for use in a lithium ion secondary battery, and to 800 to3000° C. for the electrode for use in a fuel cell or the electrode foruse in a electric double layer capacitor. In order to improveconductivity of the porous carbon, it is preferable to perform firingfrom 2000 to 3000° C. to advance graphitization.

A porous carbon electrode can be manufactured from a block copolymerconsisting of a carbon precursor polymer chain and a polymer chaincapable of forming a SiO analogue. The polymer chain capable of formingthe SiO analogue includes polysilanes having a Si—H group or alkoxylgroup in the side chains; polysiloxanes such as a polysiloxane having analkoxyl group in the side chains such as polydialkoxysiloxane;silsesquioxanes; a polymer chain having a siloxane cluster such as POSS(Polyhedral Oligomeric Silsesquioxane: polysiloxane T₈-cube).

When such a porous carbon forming material is fired, formed is ananocomposite consisting of a carbon phase, in which a structure havingmicro polymer phases is retained, and a phase of a SiO analoguematerial. When the nanocomposite is subjected to acid or alkalitreatment so that the SiO phase is selectively decomposed and removed, aporous carbon used for a carbon electrode can be provided. This formingmethod can prevent the nanopores from being collapsed through thermaldeformation during firing.

The carbon electrode formed in such a manner and having regularlyarranged nanopores can be used well for the carbon electrode for anelectrochemical cell such as a lithium ion secondary battery, anelectric double layer capacitor and a fuel cell because an electrolytesolution penetrates well into the electrode, bringing good liquidcommunication. In addition, since the pores have a uniform and finesize, a local defective structure such as a large pore may not beproduced even if the thickness of the electrode is made thin. This isadvantageous for making a fuel cell or the like thinner.

In order to manufacture a porous carbon electrode having a bicontinuousstructure such as an OBDD structure or Gyroid structure, the volumefraction of one polymer phase in a block copolymer should be set to 20to 80%, more preferably 45 to 75%, more preferably 55 to 75%, and stillmore preferably 60 to 70%. In particular, it is preferable that thevolume fraction of one polymer phase be set to 62 to 67% in the case ofOBDD structure. An OTDD structure has a third continuous phase formed atthe interface of the OBDD structure. The OTDD structure can be formedfrom a triblock copolymer consisting of three kinds of polymer chains.In the case where the OTDD structure is formed, the volume fraction ofthe third phase should be set to 40 to 70%, more preferably 45 to 55%.At the same time, (the volume fraction of the A phase)/(the volumefraction of the B phase) should be set to 0.7 to 1.3, preferably 0.9 to1.1, more preferably 1.

The porous carbon electrode manufactured from a block copolymer having astructure having micro polymer phases has a three-dimensional networkstructure different from that of the conventional porous structuremanufactured by sintering fine particles. A three-dimensional networkstructure manufactured from a structure having micro polymer phases hascorrelation distances at both 2√{square root over (3)} times and 4 timesa radius of gyration of cross section of constituent microdomains. Thecorrelation distance can be measured by, for example, X-ray small-anglescattering measurement, neutron scattering measurement and lightscattering measurement or the like. A primary scattering peak betweenmicrodomains appears at the position where the radius of gyration ofcross section of constituent microdomains is doubled. In the case of thethree-dimensional network structure shown in a conventional fineparticle sintered body, scattering peaks of high order between particlesappear at the positions of √{square root over (2)} times and √{squareroot over (3)} times with respect to the double the radius of gyrationof cross section. On the other hand, in the case of thethree-dimensional network structure of the present invention, scatteringpeaks of high order appear at the positions of √{square root over (3)}times and 2 times.

The three-dimensional network structure manufactured from a structurehaving micro polymer phases is more regular and has less structuraldefects compared to the three-dimensional network structure shown in aconventional fine particle sintered body. When such a porous electrodeexhibits a regular three-dimensional network structure is used in asecondary battery and capacitor, excellent charge-and-dischargecharacteristics and repeating characteristics can be given. Even whenthe electrode is used in a fuel cell, good output characteristics can begiven. Incidentally, change in molecular weight of a block copolymer orgraft copolymer can freely control the pore size of a porous moldedproduct, making it possible to manufacture a porous electrode adequatefor the purpose.

A porous structure constituted by a hole-conductive orelectron-conductive polymer, such as polyaniline, polyparaphenylene,polythiophen and polypyrrole, can be used as an electrode for anelectrochemical element such as an electrochromic element. These porousstructures can also be used as an electrode for a lithium ion secondarybattery, an electric double layer capacitor and a fuel cell.

An example in which a porous carbon electrode of the present inventionis applied to a direct methanol fuel cell will be described. The directmethanol fuel cell uses a carbon electrode having a three-layeredstructure of a methanol-permeating layer, a methanol-evaporating layerand a catalytic layer, in which optimum pore sizes are different forcarbon electrode in each layer. It is difficult to form a multilayeredcarbon electrode, in which pore sizes are precisely controlled in eachlayer, with a conventional carbon cloth or carbon particle-coating film.On the other hand, with the porous carbon electrode formed from a blockcopolymer having a thermally decomposable polymer and a carbon precursorpolymer, adjusting the molecular weights of the polymers can controlpore sizes precisely as already described. In addition, such a carbonelectrode has very uniform pores and hardly has defects such as largerpores, so that the electrode can be made thinner, which enables to makethe entire thickness of the cell thinner.

FIG. 7 shows a conceptual diagram of a direct methanol fuel cell. Asshown in FIG. 7, formed on the anode (fuel gas) side of the cell is amultilayered-structure of the anode catalytic electrode 11, thefuel-evaporating layer 12 and the fuel-permeating layer 13, each ofwhich is porous, and formed on the cathode (liquid fuel) side of thecell is a laminate of the cathode catalytic electrode 14 and thewater-holding gas channel 15, each of which is porous, and further theelectrolyte film 16 made of a proton conductor is interposed between theanode catalytic electrode 11 and cathode catalytic electrode 14.

It is preferable to set the pore size of the outermost fuel-permeatinglayer 13 and water-holding gas channel 15 to 0.1 μm to 10 μm. If thepore size is too small, permeability or penetrating property isdeteriorated, whereas, if the pore size is too large, it is impossibleto make the cell thinner. It is preferable to set the pore size of thefuel-evaporating layer 12 to 50 nm to 200 nm, and those of the anodecatalytic electrode 11 and the cathode catalytic electrode 14 to 10 to100 nm. In any member, if the pore size is too large, the liquid fuel islikely to soak into the member, whereas, if the pore size is too small,penetrating property of the fuel gas is deteriorated. In any layers, 60%or more, more preferably 70% or more of pore content is preferred. It ispreferable to set the thickness of the fuel-evaporating layer 12, anodecatalytic electrode 11 and cathode catalytic electrode 14 to 1 to 10 μm.If the thickness is too small, crossover of the fuel gas is increased,which lowers efficiency. If the thickness is too large, mass transfer inthe cell is inhibited, so that high output current density cannot begiven. As the electrolyte film 16, fluoropolymer having a generalsulfonic group, polybenzimidazole, a metal oxide or the like can beemployed.

Noble metal particles are loaded in the electrodes: Pt particles or thelike for the anode catalytic electrode 11, and Ru particles or the likefor the cathode catalytic electrode 14. Such a particle-loaded porouselectrode can be manufactured as follows. For example, a salt or complexof a noble metal is mixed with a block copolymer, followed by forming astructure having micro polymer phases, and then the block copolymer ismade porous, during which the block copolymer is affected with formalinor fired in hydrogen or inert gas atmosphere, thereby producing noblemetal particles.

It is also possible to use a method in which a film made of a blend ofan A–B block copolymer including a metal particle and an A–B blockcopolymer is formed, followed by forming a structure having micropolymer phases, and then the film is made porous. The method makes itpossible to segregate the metal particles covered with polymer on theinterface between the A polymer phase and B polymer phase on theoccasion of formation of the structure having micro polymer phases. Whenthe structure is made porous, the metal particles can be locallydistributed on the surface of the remained polymer phase. Such acatalyst electrode can exhibit high catalytic ability, since it has ahigh specific surface area and a high catalyst density with evendistribution.

In the present invention, a porous carbon structure can also bemanufactured by the following method. This method comprises steps of:mixing a precursor of thermosetting resin, a surfactant, water and oil,thereby preparing a microemulsion; curing the precursor of thermosettingresin in colloidal particles dispersed in the microemulsion; removingthe surfactant, water and oil from the colloidal particles, therebyforming porous structures of cured thermosetting resin; and carbonizingthe porous structures to form porous carbon structures.

As the precursor of thermosetting resin, phenol derivatives, resorcinolderivatives, furfuryl alcohol or the like can be employed. Across-linking agent such as titanium trichloride, boric acid or the likemay be added, if desired. As the oil, a hydrophobic solvent such asisooctane, hexane, petroleum ether or the like can be employed.

Examples of the surfactant include: a block copolymer or graft copolymerconsisting of a hydrophilic polymer chain and hydrophobic polymer chainsuch as a block copolymer of polypropylene oxide and polyethylene oxide;polyethylene oxide to which terminal a long-chain alkyl group isintroduced such as polyoxyethylene lauryl ether; an anionic surfactantcomprising a long-chain alkyl group to which terminal a sulfonate,phosphate or carboxylate is introduced such as sodiumdodecylbenzenesulfonate; a cationic surfactant such as a long-chainammonium salt, a long-chain pyridinium salt or a long-chain imidazoliumsalt, for example, cetyltrimethylammnonium chloride,cetyldimethybenzyl-ammnonium chloride and cetylpyridinium bromide; afluorine-based surfactant.

In the colloidal particles dispersed in the microemulsion, a structurehaving micro polymer phases comprising the precursor of thermosettingresin and the surfactant is formed. The structure having micro polymerphases has a relatively large size of several tens of nanometers toseveral tens of micrometers, and can be formed into a structure of dot,lamella, cylinder or three-dimensional network or a mixed structurethereof. Therefore, when the precursor of thermosetting resin in thecolloidal particles is cured, then the surfactant, water and oil areremoved from the colloidal particles to form porous structures of curedthermosetting resin, and then the porous structures are carbonized, aporous carbon structures having relatively large pores can bemanufactured.

In addition, when the structure having micro polymer phases relativelylarge in size which is formed using a surfactant and the structurehaving micro polymer phases of the order of sub-nanometer or so arecombined, it is possible to form a porous carbon structure whosestructure is controlled hierarchically in the range of sub-nanometer toseveral tens of micrometers. Typically, it is possible to provide aporous carbon structure of a spherical particle of several tens ofmicrometers in which pores of several micrometers are formed and furtherpores of several tens of nanometers or less are contained. When such aporous carbon structure is applied to a lithium ion secondary battery oran electric double layer capacitor, the nanopores of sub-nanometer serveas occlusion sites for lithium and absorption sites for ions, and thepores having a larger size serve to permeate an electrolyte solutionwell. Therefore, it makes possible to improve charge-and-dischargerepeating characteristics and output current density.

In the above method, when a microemulsion is prepared using a carbonprecursor as a surfactant along with adding a metal oxide gel, acomposite of the surfactant and metal oxide gel is formed by removingthe solvent, and then the composite is fired, a composite consisting ofcarbon and metal oxide gel can be formed. This method has an advantagethat nanopores in the carbon are retained well by the metal oxide gel.If desired, the metal oxide gel may be removed by means of acid oralkali.

When a low-molecular weight surfactant having a hydrophobic groupconsisting of a long-chain alkyl group is used as a surfactant in theabove method, it is possible to manufacture a porous carbon structure inwhich cylindrical nanopores of uniform pore size, in the range ofsub-nanometer to several nanometers or so, are arranged in a honeycombconfiguration. An average pore size of the pores is preferred to be 0.1to 10 nm, more preferably 0.3 to 5 nm. Examples of the low-molecularweight surfactant include: an anionic surfactant comprising a long-chainalkyl group to which terminal a sulfonate, phosphate or carboxylate isintroduced such as sodium dodecylbenzenesulfonate; and a cationicsurfactant such as a long-chain ammonium salt, a long-chain pyridiniumsalt or a long-chain imidazolium salt, for example,cetyltrimethylammnonium chloride, cetyldimethybenzyl-ammnonium chlorideand cetylpyridinium bromide; a fluorine-based surfactant. When thehoneycomb porous carbon is employed as the carbon negative electrode ofa lithium ion secondary battery, nanopores is efficiently occluded bylithium, making it possible to achieve high capacity. When the honeycombporous carbon is employed as the carbon electrode of an electric doublelayer capacitor, it is possible to increase capacity if the size ofnanopores is formed as small as the ionic radius of electrolyte. Thehoneycomb porous carbon also has high absorption ability for a gas suchas hydrogen.

In the above method, when a surfactant having two or more long-chainalkyl groups is employed, a fibrous or acicular carbon structure can bemanufactured. Such a carbon structure can be employed as a gasabsorption material, or filler for imparting conductivity orreinforcing. The acicular carbon can suitably used for the emitter ofFED.

When a perylene derivative is used as a carbon precursor in the abovemethod, acicular carbon or honeycomb porous carbon can be manufactured.An example of the perylene derivative includes 9,10-dosubstitutedperyleneimide in which a long-chain alkyl group having an ionic group orhydrophilic group such as a hydroxyl group, carboxyl group, sulfonicacid group at a terminal, or a polyether group such as oligoethyleneoxide group is introduced. When the perylene derivative is employed,formed is a structure in which columns formed by the perylene skeletonsand columns of substituents such as a long-chain alkyl group orpolyether group are alternately arranged. When the structure is fired,columns of substituents are selectively evaporated, thus acicular carbonor honeycomb porous carbon can be provided. In this method, a metaloxide gel such as a silica sol may be used together. In the case where ananostructure of a carbon precursor in the presence of a surfactant in aliquid phase, performing supercritical drying is preferred because thenanostructure is not destroyed during drying.

A case where a porous structure of the present invention is applied to aprecise filter in a sheet form or hollow fiber form will be described.Such a filter can be manufactured in the following manner. First, usinga pattern forming material comprising a block copolymer containing apolymer chain that can be decomposed by energy beam irradiation, a sheetor a hollow fiber is manufactured by casting or melt extrusion using amouthpiece. Alternatively, the pattern forming material may be appliedby dip coating to the surface of a tube comprising a homopolymer thatcan be decomposed by energy beam irradiation. Then, if required,annealing is performed to form a phase-separated structure in the film.The phase-separated structure is preferred to have a continuous phasestructure such as a cylindrical structure, bicontinuous structure, etc.,in which the bicontinuous structure is particularly preferable in viewof film strength. Bicontinuous structure includes an OBDD structure, aGyroid structure, a T-surface structure, lamella catenoid structure, orthe like. The OBDD structure or Gyroid structure is particularlypreferable because of low flow resistance. The sheet or hollow fiber, inwhich the phase-separated structure is formed in such a manner, isirradiated with an electron beam, thereby decomposing one polymer phasein the phase-separated structure. Thereafter, the sheet or hollow fiberis etched to manufacture a filter in a sheet form or hollow fiber form.

The porous structure constituting the filter formed of a pattern formingmaterial of the present invention is preferred to have an aggregatedstructure of domains each having a radius of gyration of 50 μm or lesshaving a periodical porous structure comprising unit cells each having aradius of gyration of 10 to 500 nm. Among periodical porous structures,preferred is one having continuous pores formed by removing at least onephase in a bicontinuous phase-separated structure, and particularlypreferred is a porous structure formed by removing at least one phase ina OBDD structure or Gyroid structure. Although there is not anyparticular limitation with respect to the pore size, it shouldpreferably be in the range of 5 to 200 nm, more preferably 10 to 50 nm.If the pore size is too small, flow resistance will be increased, whichmakes it impossible to use the filter practically. If the pore size istoo large, dispersion of pore size distribution will be increased, whichmakes it also impossible to use the filter practically.

The filter according to the present invention is more preferred to havean asymmetrical structure. Specifically, preferred is an asymmetricalfilm in which a thin filter layer consisting of a pattern formingmaterial of the present invention is formed on a relatively thick,porous film having pores large in size. Such an asymmetrical structurecan improve mechanical strength as well as reduce flow resistance. Thethick, porous film having large-size pores can be manufactured asfollows. For example, using a blend of homopolymers each having the samestructure as each polymer chain constituting the pattern formingmaterial of the present invention, a sheet or a hollow fiber ismanufactured, and then at least one homopolymer is removed to form aporous film. In order to remove the homopolymer, it is possible to usemethods of: simple extraction with a solvent; selective etching by RIE;irradiation with an energy beam such as an electron beam and subsequentextraction with a solvent or thermal decomposition/evaporation. Then, apattern forming material according to the present invention is formed onthe porous film by dip coating. Thereafter, using a similar method tothat described above, a filter in a sheet form or hollow fiber formhaving an asymmetrical structure is manufactured.

Another method may be used in which a pattern forming material is formedon a tube consisting of a blend of homopolymers by dip coating, and thenthe tube is irradiated with energy beam and etched, thereby formingsimultaneously a relatively thick porous film having large pore size of0.5 to 5 μm or so and a thin filter layer to provide an asymmetricalstructure, which is very effective in improving a permeation rate.

The filter of the present invention can be suitably used as a filtrationmembrane, a dialysis membrane, a gas separation membrane, a reverseosmosis membrane, an ultrafiltration membrane, a microfiltrationmembrane or a blood purification membrane. In most of theseapplications, the filter is used in the form of filter module.

A case where a porous structure of the present invention is applied toan ultrafine fiber of the order of nanometers having a thickness of 10to 100 nm, or to a porous fiber having pores of the order of nanometerswill be described. These ultrafine fiber and porous fiber can bemanufactured, for example, in the following manner. First, using apattern forming material comprising a block copolymer having a polymerchain that can be decomposed by energy beam irradiation, a precursorfiber having a diameter of 10 to 100 μm is manufactured by meltextrusion using a mouthpiece. The precursor fiber may be woven into afabric. Then, if required, annealing is performed to form aphase-separated structure in the fiber. The phase-separated structure ispreferred to have a continuous phase structure such as a sea-islandstructure, a cylindrical structure, a lamella structure or abicontinuous structure. The precursor fiber or fabric in which thephase-separated structure is formed in such a manner is irradiated withan energy beam selected especially from an electron beam, γ-ray or X-rayso as to decompose one phase in the phase-separated structure, followedby etching, thus an ultrafine fiber or porous fiber is provided.

The relationship between the phase-separated structure of the patternforming material and the ultrafine fiber or porous fiber to bemanufactured is as follows. In the case of the sea-island structure, aporous fiber having closed cells is formed. In the case of thecylindrical structure, an ultrafine fiber having a thickness of theorder of nanometers having a diameter of 10 to 200 nm is formed. In thecase of the lamella structure, an ultrafine fiber in a form of thinpiece having a thickness of 10–200 nm is formed. In the case of thebicontinuous structure, a porous fiber in which unit cells of 10 to 200nm in size are periodically arrayed is formed.

These ultrafine fiber and porous fiber may contain, as alreadydescribed, a plasticizer, an antioxidant, a light stabilizer, a coloringagent (dye or pigment), an antistatic agent, a conductive agent, alubricant, a release agent, a flame retardant, an auxiliary flameretardant, etc.

The ultrafine fiber and porous fiber as well as a fabric prepared fromthese fibers has a large surface area, so that they can be used forvarious filters, a carrier medium for bacteria, a deodorant, anabsorption material, a wiping material, a water-repellent, etc. Inaddition, the fabric manufactured from the fiber of the presentinvention has texture and pleasant feeling that cannot be found in theconventional fabric.

In the present invention, a capacitor having a high capacity can bemanufactured. The method comprises the steps of: forming a film made ofa blend of a polymer including a metal particle and a block copolymer orgraft copolymer; allowing the film to form a lamella structure havingmicro polymer phases and segregating the metal particles covered withthe polymer in a central portion of each polymer phase in the lamellastructure; and aggregating the metal particles to form a metal layer inthe central portion of each polymer phase in the lamella structure.

The method will be described with reference to FIGS. 8A to 8C. In thesefigures, the numeral 21 represents the A–B block copolymer, the numeral22 represents the A or B homopolymer, and the numeral 22 represents themetal particle. First, the A–B block copolymer, A polymer including themetal particle and B polymer including the metal particle are blended.Use is a block copolymer having a composition ratio in the range of70:30 to 30:70, preferably 55:45 to 45:55, so that it forms a lamellastructure. The material is dissolved in a solvent, followed by castingslowly. Preferred solvent is one having a low boiling point such as THF,acetone, and toluene. The surface of the cast film is planarized, andthen the film is extended with a roller so as to give a thickness of 0.1to 1 mm or so. The film is referred to as a first film.

Further, the blend of the A homopolymer and A homopolymer including ametal particle is dissolved in a solvent to manufacture a cast film. Thefilm is referred to as a second film. Likewise, the blend of the Bhomopolymer and B homopolymer including a metal particle is dissolved ina solvent to manufacture a cast film. The film is referred to as a thirdfilm.

The second film, the first film and the third film are laminated in thisorder, followed by annealing in an oven. A lamella structure is formedthrough microphase separation, thus the metal particle covered with theA homopolymer is segregated on the A phase, and the metal particlecovered with the B homopolymer is segregated on the B phase,respectively, in which the metal particles are present in the centralportion of each polymer phase in the lamella structure. Next, when thetemperature is raised, the main chain of the polymer covering the metalparticle is broken, thus the metal particles are aggregated to form acontinuous metal film. In practice, it is assumed that migration andaggregation of two metal particles take place simultaneously during theannealing. Metal thin films are formed on the both surfaces of themanufactured film by sputtering to form electrodes, and then the film iscut into an arbitrary size.

The method can easily form a lamellar structure having uniformintervals. Since the microphase separation of the block copolymer isutilized, a lamella structure in which a number of layers arealternately laminated can be manufactured by only annealing. At thattime, the metal can be arranged in the center portion of the layersformed via microphase separation. In addition, the lamellar structuremay not cause short-circuit between metal layers. The method can makethe distance between the opposite electrodes in capacitor very short aswell as hold the electrodes in an even spacing. Therefore, the capacitorcan accumulate many charges in a small volume, thus it exhibits veryhigh performance compared to the conventional capacitor.

EXAMPLES

Hereinafter, the present invention will be specifically described basedon examples. It should be noted that the present invention is notlimited to these examples.

Synthesis Example

A diblock copolymer (1) of polystyrene (PS) and polymethyl methacrylate(PMMA) is synthesized by living anion polymerization. Molecular sievesand activated alumina are added to polystyrene monomer and polymethylmethacrylate monomer, respectively, followed by leaving to stand for twodays to remove water and an inhibitor. These monomers are distilledunder reduced pressure, and then the atmosphere is replaced with argongas. Dehydrated THF (Wako Junyaku Co., Ltd.) is prepared as a reactionsolvent to which metallic sodium is added as a dehydrating agent, andthen reflux is performed for two days. As a polymerization initiator,sec-butyl lithium (Kanto Kagaku Co., Ltd.) is employed.

As a polymerization apparatus, a pressure reactor (Taiatsu Glass Co.,Ltd.) is employed. The reaction is carefully performed under apressurized argon atmosphere of 4 atm so as to prevent outside air fromentering the reaction system. While flowing argon, the dehydrated THFand polymerization initiator are added. Then, the reaction system iscooled to −78° C. with dry ice/ethanol. A small quantity of styrenemonomer is added to the reaction system. After confirming that thereaction solution turned into orange color, the reaction is continuedfor 30 minutes. A small quantity of the reaction solution is taken outto measure a molecular weight by gel permeation chromatography (GPC),and on the basis of the molecular weight measured, the quantity ofstyrene monomer to be added for obtaining a polystyrene block having adesired molecular weight is calculated. Based on the calculation, astyrene monomer is added to the reaction system and the reaction isperformed for 30 minutes. A small quantity of the reaction solution istaken out, and it is confirmed by GPC that a desired molecular weight isobtained. Thereafter, a small quantity of 1,1′-diphenylethylene isadded, and then a requisite quantity of methyl methacrylate monomer toobtain a polymethyl methacrylate block having a desired molecular weightis added dropwise to the reaction system and the reaction is performedfor 30 minutes. A small quantity of the reaction solution is taken out,and it is confirmed by GPC that a desired molecular weight is obtained.After a small quantity of methanol is added dropwise to terminate thereaction, the reactor is opened. The reaction solution is dropped tomethanol for reprecipitation, followed by filtration and drying, therebyto obtain the diblock copolymer (1).

The molecular weight of each block constituting the diblock copolymer(1) is 65,000 for polystyrene, and 13,200 for polymethyl methacrylate.Further, the molecular weight distribution (Mw/Mn) is 1.04.

In the following examples, there are some cases that a diblock copolymerof PS-PMMA other than the diblock copolymer (1) may be employed. Also,each diblock copolymer is synthesized by living anion polymerization inthe same manner as the aforementioned synthesis example except that thequantities of styrene monomer and methyl methacrylate monomer arechanged.

Example 1

Two wt % of the diblock copolymer (1) is dissolved in propylene glycolmonoethyl ether acetate (PGMEA), followed by filtering the solution, andthen an SiO substrate is spin-coated with the solution at 2,500 rpm. Thesubstrate is heated to 110° C. for 90 seconds to evaporate the solvent.Thereafter, the substrate is placed in an oven, and annealing isperformed in a nitrogen atmosphere at 210° C. for 10 minutes,subsequently at 135° C. for 10 hours. Since the temperature of 210° C.is just below a temperature that decomposition of the acrylic blocktakes place, the short time annealing enables to flatten the film withdissipating hysteresis after spin-coating. Further, the annealing at thetemperature of about 135° C. enables to promote microphase separation ofthe diblock copolymer efficiently, so that a film having micro polymerphases is formed.

Reactive ion etching (RIE) is performed to the sample under theconditions of CF₄, 0.01 Torr, 150 W of progressive wave, and 30 W ofreflected wave. Under the etching conditions, since the ratio of etchrates between PS and PMMA constituting the film having micro polymerphases is 1:4 or more, PMMA is selectively etched and further theexposed underlayer is etched by use of the remaining PS pattern as amask. Thereafter, ashing is performed to the sample under the conditionsOf O₂, 0.01 Torr, 150 W of progressive wave, and 30 W of reflected waveto remove the organic substance (the mask formed of PS).

As a result, holes having a diameter of 12 nm and a depth of 15 nm areformed over the entire surface of the SiO substrate having a diameter of3 inches at a density of about 700/μm² and at approximately regularintervals. The substrate can be used as a substrate for a hard disk.

In addition, a film having micro polymer phases is formed in the samemanner as described above except that 10 wt % of dioctyl phthalate as aplasticizer is added to the diblock copolymer (1) and the heat treatmentconditions are changed to at 210° C. for 10 minutes, subsequently at135° C. for one hour, and RIE is performed under the same conditions asdescribed above. As a result, a pattern of holes can be formed on thesubstrate similar to those described above. Thus, it is possible togreatly shorten the heat treatment time by adding the plasticizer to thediblock copolymer.

Example 2

A film having micro polymer phases is formed on a glass substrate in thesame manner as described in Example 1. The film having micro polymerphases is irradiated with an electron beam over the entire surface underthe conditions of an accelerating voltage of 50 kV and an exposure doseof 100 μC/cm², thus the main chain of the PMMA is cut. The film havingmicro polymer phases is developed with a developer (3:7 mixed solutionof MIBK and IPA) for an electron beam resist for 60 seconds, followed byrinsing with IPA, thus the PMMA whose main chain is cut by electron beamis removed. Then, using a pattern mainly consisting of remaining PS as amask, the substrate is etched with hydrofluoric acid for one minute.Thereafter, the substrate is subjected to an ultrasonic washing inacetone, thus the remaining mask is removed.

As a result, holes having a diameter of 15 nm and a depth of 12 nm areformed over the entire surface of the glass substrate at a density ofabout 700/μm² and at approximately regular intervals. By making use ofthis method, the whole steps can be performed by wet processes. As inthe case of Example 1, the substrate can be used as a substrate for ahard disk.

When the pattern formation is performed in the same manner as describedabove except that the substrate is irradiated with X-ray having awavelength of 0.154 nm under an exposure dose of 1 J/cm² in place of theelectron beam irradiation, holes having a diameter of 15 nm and a depthof 12 nm are formed over the entire surface of the glass substrate at adensity of about 700/μm² and at approximately regular intervals.

Example 3

Using a diblock copolymer (2) (polystyrene: Mw=10,600, polymethylmethacrylate: Mw=35,800; Mw/Mn=1.07), a film having micro polymer phasesis formed on a magnetic film formed on a substrate having a diameter of3 inches in the same manner as described in Example 1. The film havingmicro polymer phases is irradiated with an electron beam to cut the mainchain of PMMA. The film having micro polymer phases is developed with adeveloper for electron beam resist, thus PMMA whose main chain is cut byelectron beam is removed. Then, using a pattern mainly consisting ofremaining PS as a mask, the substrate is etched with hydrochloric acidfor one minute. Thereafter, the substrate is subjected to an ultrasonicwashing in acetone, thus the remaining mask is removed.

As a result, projections of magnetic film having a diameter of 15 nm anda height of 12 nm are formed over the entire surface of the substrate ata density of about 650/μm² and at approximately regular intervals. Bymaking use of this method, a magnetic film can be left remained in anisland configuration by directly processing the film in wet processes.

Example 4

A quartz substrate is spin-coated with a polystyrene film having athickness of 500 nm as a lower pattern transfer film, on which analuminum film having a thickness of 10 nm is deposited as an upperpattern transfer film. The aluminum film is spin-coated with diblockcopolymer (3) (polystyrene: Mw=144,600, polymethyl methacrylate:Mw=70,700; Mw/Mn=1.07) having a thickness of 80 nm. Then, annealing isperformed in the same manner as in Example 1 to form a film having micropolymer phases.

RIE is performed to the sample under the conditions of CF₄, 0.01 Torr,150 W of progressive wave, and 30 W of reflected wave, thus PMMA in thefilm having micro polymer phases is etched selectively and further thealuminum film is etched by use of remaining PS pattern as a mask.Thereafter, ashing is performed to the sample under the conditions ofO₂, 0.01 Torr, 150 W of progressive wave, and 30 W of reflected wave toremove the mask consisting of remaining PS and the polystyrene filmexposed at the portions where the aluminum film has been etched. RIE isperformed again to the sample under the conditions of CF₄, 0.01 Torr,150 W of progressive wave, and 30 W of reflected wave, thus the upperaluminum film and the exposed portions of the quartz substrate isetched. Ashing is performed again to the sample under the conditions ofO₂, 0.01 Torr, 150 W of progressive wave, and 30 W of reflected wave toetch the remaining polystyrene.

As a result, holes having a very high aspect ratio, i.e., a diameter of110 nm and a depth of 1200 nm are formed over the entire surface of thequartz substrate at a density of 35/μm².

Example 5

An SiO₂ film having a thickness of 500 nm is formed on a silicon wafer,and then the SiO₂ film is coated with a toluene solution of polysilane(Mw=12000, x=0.4) represented by the following chemical formula,followed by baking to form a pattern transfer film consisting ofpolysilane having a thickness of 100 nm.

The pattern transfer film is coated with a diblock copolymer (4)(polystyrene: Mw=12,000, polymethyl methacrylate: Mw=28000), followed bybaking at 90° C. for two minutes to form a 40 nm-thick film having micropolymer phases.

RIE is performed to the sample under the conditions of CF₄, 0.01 Torr,150 W of progressive wave, and 30 W of reflected wave, thus PMMA in thefilm having micro polymer phases is etched selectively. Then, thepolysilane film is etched by use of the remaining PS pattern as a maskunder the conditions of HBr flow rate of 50 sccm, vacuum degree of 80mTorr and excitation power of 200 W to transfer the pattern. Since themask consisting of PS is left remained on the remaining polysilane film,it is found that there is a sufficient etch rate ratio between them.Then, by use of the pattern of polysilane film as a mask, the SiO₂ filmis etched under the conditions of C₄F₈ flow rate of 50 sccm, CO flowrate of 10 sccm, Ar flow rate of 100 sccm, O₂ flow rate of 3 sccm,vacuum degree of 10 mTorr, and excitation power of 200 W to transfer thepattern. Since the polysilane film is left remained on the remainingSiO₂ film, it is found that the polysilane film is sufficient etchresistance. The remaining polysilane film can be easily removed with anaqueous organoalkali solution or a diluted hydrofluoric acid solution.

Example 6

A gold electrode is deposited on 10-inch glass substrate used for asubstrate of a field emission display, an SiO₂ film as a lower patterntransfer film is applied to the entire surface of the gold electrode,and further an aluminum film having a thickness of 20 nm as an upperpattern transfer film is deposited on the lower pattern transfer film.Then, a diblock copolymer (5) (polystyrene: Mw=127,700, polymethylmethacrylate: Mw=1,103,000; Mw/Mn=1.30) and polystyrene homopolymer(Mw=45000, Mw/Mn=1.07) are blended together at a weight ratio of 21:79,then the blend is dissolved in ethylcellosolve acetate (ECA) at a solidcontent of 5 wt %, followed by filtration. The aluminum film isspin-coated with the solution, followed by drying at 110° C. to form apolymer film having a thickness of 970 nm. In the same manner as inExample 1, the substrate is placed in an oven, and annealing isperformed in a nitrogen atmosphere at 210° C. for 10 minutes,subsequently at 135° C. for 10 hours to form a film having micro polymerphases.

RIE is performed to the sample under the conditions of CF₄, 0.01 Torr,150 W of progressive wave, and 30 W of reflected wave, thus PMMA in thefilm having micro polymer phases is etched selectively and further thealuminum film is etched using the remaining PS pattern as a mask totransfer the pattern. Using the pattern of PS and the pattern ofaluminum film as a mask, exposed portions of the SiO film are etchedwith hydrofluoric acid to transfer the pattern. Since the pattern ofaluminum film is covered with a pattern of PS, it is not damaged.Thereafter, ashing is performed with an O₂ asher to remove the remainingPS pattern.

As a result, holes having a diameter of about 840 nm can be formed at adensity of about 23000 per pixel of 300 μm×100 μm. Distribution of holesize is found uniform within the range of ±10%. This is attributed tothe uniformity in molecular weight of the diblock copolymer. Since thediblock copolymer exists in the sea of styrene homopolymer in thepolymer film employed as a mask, the arrangement of formed holes isfound random. Therefore, it is advantageous in application to a displayto prevent an interference fringe due to regular arrangement ofelectrodes.

The structure formed by the method in this example can be applied to afield emission display (FED) as well as a gate electrode of a porousgate transistor display, etc.

In addition, a film having micro polymer phases is formed in the samemanner as described above except that 10 wt % of dioctyl phthalate isadded as a plasticizer to the blend of diblock copolymer and polystyrenehomopolymer and the heat treatment conditions are changed to at 210° C.for 10 minutes, subsequently at 135° C. for one hour, and RIE isperformed under the same conditions as described above. As a result, apattern of holes can be formed on the substrate similar to thosedescribed above. Thus, it is possible to greatly shorten the heattreatment time by addition of the plasticizer.

Example 7

A 10 wt % solution of a diblock copolymer (6) (polystyrene: Mw=135,000,PMMA: Mw=61,000, Mw/Mn=1.10) in THF is poured in a Teflon Petri dish,which solution is allowed to dry slowly over 14 days in a desiccator toform a film. The thickness of the film is 0.2 mm. The film is furthervacuum dried for 3 days. An ultra-thin film is cut out of this film toobserve with a transmission electron microscope. As a result, it isconfirmed that the PS phase and the PMMA phase are respectively formedcontinuously into a three-dimensional bicontinuous structure.

The film is irradiated with an electron beam under the conditions ofaccelerating voltage of 2 MV and exposure dose of 10 kGy, and then thefilm is developed with a developer for electron beam resist, which isreduced is solubility of PS by addition of IPA, followed by vacuumdrying. An ultra-thin film is cut out of the film to observe again witha transmission electron microscope. As a result, it is confirmed thatthe PMMA phase is removed and the PS phase is formed into a spongycontinuous structure. It is confirmed that the structure is almost thesame as the three-dimensional bicontinuous structure observed first.

The film is constituted by a PS phase that is three-dimensionallycontinued with interposing regularly continued cells of the order ofnanometers. Such a structure can be applied to a separator for a polymerbattery or capacitor.

Example 8

A diblock copolymer (1) is dissolved by 1 wt % in methylene chloride,followed by filtering, and then 1 wt % based on the weight of thepolymer of tetrabutylammonium hexachloroplatinate (IV) is added. Thesolution is cast on a SiO substrate having a diameter of 3 inches toform a film having a thickness of 20 nm. The substrate is heated at 110°C. for 90 seconds to evaporate the solvent. Then, the substrate isplaced in an oven and subjected to annealing at 150° C. for 3 hours in anitrogen atmosphere to form a film having micro polymer phases. At thattime, tetrabutylammonium hexachloroplatinate (IV) is segregated in PMMA.After the film having micro polymer phases is rinsed with formaldehydereducing solution, the film is again subjected to annealing at 200° C.for one hour, thereby reducing the tetrabutylammoniumhexachloroplatinate (IV) to platinum.

RIE is performed to the sample under the conditions of CF₄, 0.01 Torr,150 W of progressive wave, and 30 W of reflected wave, thus PMMA isetched selectively and further the underlying SiO substrate is etched byuse of the remaining PS pattern as a mask. Thereafter, ashing isperformed under the conditions of O₂, 0.01 Torr, 150 W of progressivewave, and 30 W of reflected wave to remove the remaining PS mask.

As a result, holes having a diameter of 15 nm and a depth of 10 nm areformed over the entire surface of the SiO substrate having a diameter of3 inches at a density of about 2000/μm² and at approximately regularintervals. Furthermore, platinum particles are deposited at the bottomsof the holes. By making use of the substrate, a magnetic material, forexample, can be grown over the platinum particles deposited at thebottoms of the holes as nuclei, and therefore the substrate isapplicable to a substrate for a hard disk.

Example 9

A diblock copolymer (1) is dissolved in DMF by 1 wt %, followed byfiltering, and then a DMF solution, in which 1 wt % based on the weightof the polymer of tetrabutylammonium hexachloroplatinate (IV) isdissolved, is added and mixed homogeneously. A DMF solution of sodiumborate hydride is added to the solution to reduce the tetrabutylammoniumhexachloroplatinate (IV), thereby precipitating platinum particleshaving an average particle size of 4 nm. A SiO substrate having adiameter of 3 inches is spin-coated with the solution to form a filmhaving a thickness of 25 nm. The substrate is heated at 110° C. for 90seconds to evaporate the solvent. Then, the substrate is placed in anoven and subjected to annealing in a nitrogen atmosphere at 200° C. for3 hours to form a film having micro polymer phases. At that time,platinum particles are segregated in PMMA.

RIE is performed to the sample under the conditions of CF₄, 0.01 Torr,150 W of progressive wave, and 30 W of reflected wave, thus PMMA isselectively etched and further the underlying SiO substrate is etched byuse of the remaining PS pattern as a mask. Thereafter, ashing isperformed under the conditions of O₂, 0.01 Torr, 150 W of progressivewave, and 30 W of reflected wave, thus the remaining PS mask is removed.

As a result, holes having a diameter of 17 nm and a depth of 10 nm areformed over the entire surface of the SiO substrate having a diameter of3 inches at a density of about 2000/μm² and at approximately regularintervals. Furthermore, platinum particles are deposited at the bottomsof the holes. By making use of the substrate, a magnetic material, forexample, can be grown over the platinum particles deposited at thebottoms of the holes as nuclei, and therefore the substrate isapplicable to a substrate for a hard disk.

Example 10

A diblock copolymer (1) is dissolved by 1 wt % in methylene chloride,followed by filtering, and then 1 wt % based on the weight of thepolymer of tetrabromogold(III) cetylpyridinium salt is added. Thesolution is cast on a SiO substrate having a diameter of 3 inches toform a film having a thickness of 20 nm. The substrate is heated at 110°C. for 90 seconds to evaporate the solvent. Then, the substrate is placein an oven and subjected to annealing in a nitrogen atmosphere byraising the temperature from 100° C. to 200° C. over 3 hours to form afilm having micro polymer phases. As a result of the annealing, thetetrabromogold(III) cetylpyridinium salt is reduced, therebyprecipitating gold fine particles. At that time, the gold fine particlesare segregated in PMMA.

RIE is performed to the sample under the conditions of CF₄, 0.01 Torr,150 W of progressive wave, and 30 W of reflected wave, thus PMMA isselectively etched and further the underlying SiO substrate is etched byuse of the remaining PS pattern as a mask. Thereafter, ashing isperformed under the conditions of O₂, 0.01 Torr, 150 W of progressivewave, and 30 W of reflected wave to remove the remaining PS mask.

As a result, holes having a diameter of 15 nm and a depth of 10 nm areformed over the entire surface of the SiO substrate having a diameter of3 inches at a density of about 2000/μm² and at approximately regularintervals. Furthermore, gold particles are deposited at the bottoms ofthe holes. It is also possible to produce platinum fine particles in thesame manner as described above. By making use of the substrate, amagnetic material, for example, can be grown over the platinum particlesdeposited at the bottoms of the holes as nuclei, and therefore thesubstrate is applicable to a substrate for a hard disk.

Example 11

Two kinds of telechelic polymers, i.e., carboxyl-terminated polystyrene(Mw=83,000, Mw/Mn=1.08) represented by the chemical formula (11a) isblended with amino-terminated polymethyl methacrylate (Mw=19,600,Mw/Mn=1.03) represented by the chemical formula (11b) in equal moles,and then, dissolved in PGMEA to obtain a 2 wt % solution. Thepolystyrene and PMMA are allowed to react with each other in thesolution to prepare a diblock copolymer. The solution is filtered, andthen applied to a SiO substrate having a diameter of 3 inches by spincoating at a rate of 2,500 rpm. The substrate is heated at 110° C. for90 seconds to evaporate the solvent. Thereafter, the substrate is placedin an oven and subjected to annealing in a nitrogen atmosphere at 210°C. for 10 minutes, subsequently at 135° C. for 10 hours to form a filmhaving micro polymer phases.

RIE is performed to the sample under the conditions of CF₄, 0.01 Torr,150 W of progressive wave, and 30 W of reflected wave, thus PMMA in thefilm having micro polymer phases is etched selectively and further theunderlying substrate is etched with the remaining PS pattern being usedas a mask. Thereafter, ashing is performed under the conditions of O₂,0.01 Torr, 150 W of progressive wave, and 30 W of reflected wave toremove the remaining PS mask.

As a result, holes having a diameter of 25 nm and a depth of 16 nm areformed over the entire surface of the SiO substrate having a diameter of3 inches at a density of about 1000/μm² and at approximately regularintervals.

Example 12

Dimethylchlorosilyl-terminated polystyrene (Mw=85,000, Mw/Mn=1.04)represented by the chemical formula (12a) is blended withhydroxyl-terminated polydimethyl siloxane (Mw=16,800, Mw/Mn=1.10)represented by the chemical formula (12b) in equal moles, to which asmall quantity of triethyl amine is added, and then the blend isdissolved in PGMEA to obtain a 2 wt % solution. In the solution,polystyrene and polydimethyl siloxane are allowed to react with eachother in the presence of trimethyl amine to produce a diblock copolymer.The solution is filtered and then, is applied to a SiO substrate havinga diameter of 3 inches by spin coating at a rate of 2,500 rpm. Thesubstrate is heated at 110° C. for 90 seconds to evaporate the solvent.Then, the substrate is placed in an oven and subjected to annealing in anitrogen atmosphere at 210° C. for 10 minutes, subsequently at 135° C.for 10 hours to forming a film having micro polymer phases.

RIE is performed to the sample under the conditions of CF₄, 0.01 Torr,150 W of progressive wave, and 30 W of reflected wave. Under the etchingconditions, the etch rate ratio between PS and polydimethyl siloxanecomes to be 1:4 or more. As a result, only the polydimethyl siloxane inthe film having micro polymer phases is selectively etched, and furtherthe underlying SiO substrate is etched with using the remaining PSpattern as a mask. Thereafter, ashing is performed under the conditionsof O₂, 0.01 Torr, 150 W of progressive wave, and 30 W of reflected waveto remove the remaining PS mask.

As a result, holes having a diameter of 25 nm and a depth of 17 nm areformed over the entire surface of the SiO substrate having a diameter of3 inches at a density of about 1000/μm² and at approximately regularintervals.

Example 13

A diblock copolymer of polyphenylmethyl silane-polystyrene(polyphenylmethyl silane: Mw=12,000, polystyrene: Mw=48,000, Mw/Mn=2.1)is synthesized by the method of S. Demoustier-Champagne et al. (Journalof Polymer Science: Part A: Polymer Chemistry, Vol. 31,2009–2014(1993)).

After 1.5 wt % of the diblock copolymer is dissolved in toluene andfiltered, the solution is applied to an SiO substrate having a diameterof 3 inches by spin coating at a rate of 2,500 rpm. The substrate isheated at 110° C. for 90 seconds to evaporate the solvent. Then, thesubstrate is placed in an oven and subjected to annealing in a nitrogenatmosphere at 210° C. for 10 minutes, subsequently at 135° C. for 10hours to form a film having micro polymer phases.

RIE is performed to the sample under the conditions of CF₄, 0.01 Torr,150 W of progressive wave, and 30 W of reflected wave. Under the etchingconditions, the etch rate ratio between PS and polysilane comes to be1:4 or more. As a result, only the polysilane in the film having micropolymer phases is selectively etched, and further the underlying SiOsubstrate is etched with using the remaining PS pattern as a mask. Then,ashing is performed under the conditions of O₂, 0.01 Torr, 150 W ofprogressive wave, and 30 W of reflected wave to remove the remaining PSmask.

As a result, holes having a diameter of 12 nm and a depth of 10 nm areformed over the entire surface of the SiO substrate having a diameter of3 inches at a density of about 2400/μm² and at approximately regularintervals.

Example 14

Using masked disilane represented by the chemical formula (14a) as amonomer and phenyl methacrylate represented by the chemical formula(14b), a diblock copolymer represented by the chemical formula (14c) issynthesized by living anion polymerization. Specifically, thepolymerization is performed in a THF solution using sec-butyl lithium asan initiator, setting the reaction temperature to −78° C. and adding themonomer successively. The diblock copolymer is found to be 70,500 inweight average molecular weight (Mw), Mw/Mn=1.2, 14,500 in molecularweight of polysilane block, and 56,000 in molecular weight of polyphenylmethacrylate block.

After 1.5% weight of the diblock copolymer is dissolved in toluene andfiltered, the solution is applied to a SiO substrate having a diameterof 3 inches by spin coating at a rate of 2,500 rpm. The substrate isheated at 110° C. for 90 seconds to evaporate the solvent. Then, thesubstrate is placed in an oven and subjected to annealing in a nitrogenatmosphere at 210° C. for 10 minutes, subsequently at 135° C. for 10hours to form a film having micro polymer phases.

RIE is performed to the sample under the conditions of CF₄, 0.01 Torr,150 W of progressive wave, and 30 W of reflected wave. Under the etchingconditions, only the polysilane in the film having micro polymer phasesis selectively etched, and further the underlying SiO substrate isetched with using the remaining polyphenyl methacrylate pattern as amask. Thereafter, ashing is performed under the conditions of O₂, 0.01Torr, 150 W of progressive wave, and 30 W of reflected wave to removethe remaining polyphenyl methacrylate.

As a result, holes having a diameter of 14 nm and a depth of 10 nm areformed over the entire surface of the SiO substrate having a diameter of3 inches at a density of about 2400/μm² and at approximately regularintervals.

Example 15

Styrene-terminated polyethylene oxide macromer represented by thechemical formula (15a) (Mw=14,100, Mw/Mn=1.04) and styrene are dissolvedin THF, to which solution AIBN as a radical initiator is added, and thenthe resultant mixture is heated in an argon atmosphere at 60° C. for 60hours for radical polymerization to synthesize a graft copolymer. Thisgraft copolymer is found to be 101,000 in weight average molecularweight (MW), Mw/Mn=2.1, 16,400 in molecular weight of styrene chain, and84,600 in molecular weight of polyethylene oxide macromer unit.

After 2 wt % of the graft copolymer is dissolved in ethyl lactate andfiltered, the solution is applied to an SiO substrate having a diameterof 3 inches by spin coating at a rate of 2,500 rpm. The substrate isheated at 110° C. over 90 seconds to evaporate the solvent. Then, thesubstrate is placed in an oven and subjected to annealing in a nitrogenatmosphere at 210° C. for 10 minutes, subsequently at 135° C. for 10hours to form a film having micro polymer phases.

RIE is performed to the sample under the conditions of CF₄, 0.01 Torr,150 W of progressive wave, and 30 W of reflected wave. Under theconditions, only the polyethylene oxide in the film having micro polymerphases is selectively etched, and further the underlying SiO substrateis etched with using the remaining PS pattern as a mask. Then, ashing isperformed under the conditions of O₂, 0.01 Torr, 150 W of progressivewave, and 30 W of reflected wave to remove the remaining PS mask.

As a result, innumerable projections having a diameter of 18 nm and aheight of 10 nm are formed over the entire surface of the substrate.

Example 16

An electrolyte separator for electrochemical cell is manufactured asfollows.

First, a diblock copolymer is synthesized. To anhydrous THF distilled inthe presence of metallic sodium, α-styryl lithium is added as aninitiator, and isoprene and methyl methacrylate are successively added,thereby synthesizing a diblock copolymer comprising a polyisoprene chainand a polymethyl methacrylate chain. The diblock copolymer is found tobe 81,000 in weight average molecular weight (Mw), Mw/Mn=1.3, and 67% inweight fraction of polyisoprene unit.

A solution of the diblock copolymer is prepared and formed into a filmby casting. The film is annealed under a nitrogen gas flow at 130° C.for 5 hours to form a structure having micro polymer phases. When thestructure having micro polymer phases is observed with TEM, a Gyroidstructure having openings of about 40 nm in size is formed.

The film having a Gyroid structure is irradiated with an electron beamunder the conditions of 2 MV in accelerating voltage and 10 kGy inexposure dose, thereby cutting the main chain of the polymethacrylatephase, and, at the same time, cross-linking the polyisoprene phase(gelation). The film is rinsed with a mixed solvent of MIBK andisopropyl alcohol (volume ratio: 3.7) to remove the polymethacrylatephase. When the film is observed with TEM, it is confirmed that the filmretains the Gyroid structure and is porous with continuous pores.

The porous film is impregnated with a 1M solution of LiClO₄ (anhydride)in propylene carbonate and punched out into a disk having a diameter of0.5 cm to provide an electrolyte-impregnated porous film having athickness of about 50 μm. The electrolyte-impregnated porous film issandwiched between platinum electrodes to give a cell, which is measuredfor AC impedance using an impedance gain phase analyzer 1260(Schlumberger Instruments Co., Ltd.) at room temperature and at afrequency of 30 MHz to 0.05 Hz. Thus, ion conductivity of the cell isdetermined from σ=(1/R)(d/s), where R is electric resistance of the filmgiven by the measured AC impedance; s (cm²) is the area of the film; andd (cm) is the thickness of the film. The porous film exhibits good ionconductivity of 4.2 mScm⁻¹ at 25° C. The porous film holds theelectrolyte solution well, and hence, no liquid leakage occurs.

Further, an electrolyte-impregnated porous film is prepared in the samemanner as described above except that 3 wt %, based on the diblockcopolymer, of silica fine particles (Tokuseal P, Tokuyama Soda Co.,Ltd.) is dispersed in the solution of diblock copolymer. The resultantporous film exhibits good ion conductivity of 4.5 mScm⁻¹ at 25° C.

It is found from these results that the electrolyte-impregnated porousfilm in this example has an excellent property useful for an electrolyteseparator for an electrochemical cell such as a lithium ion secondarybattery, and for a dye-sensitizing photovoltaic cell such as anelectrochromic cell and a Gratzer cell.

Example 17

Using the same diblock copolymer comprising polyisoprene chain andpolymethyl methacrylate chain as used in Example 16, an electrolyteseparator for electrochemical cell is manufactured by melt extrusionmolding as described below.

First, a little amount (about 1 wt % based on the polymer) of avulcanizing agent is added to the diblock copolymer, and then thecopolymer is dissolved in dimethylformamide (DMF) to form a stocksolution for extrusion molding. The viscosity of the stock solution is2400 mPaòs at 40° C. The stock solution is ejected from a sheet diehaving a rectangular nozzle of 60 μm in slit width into a 40% solutionof DMF, thereby manufacturing a diblock copolymer sheet. The sheet isannealed under a nitrogen gas flow at 130° C. for 5 hours to give astructure having micro polymer phases. Thereafter, the sheet is annealedat 150° C. for 5 hours to cross-link the polyisoprene chain. The sheetis irradiated with an electron beam under the conditions of 2 MV inaccelerating voltage and 10 kGy in exposure dose. The sheet is rinsedwith a mixed solvent of MIBK and isopropyl alcohol (volume ratio: 3.7)to obtain a porous sheet.

The porous sheet is impregnated with a 1M solution of LiClO₄ (anhydride)in propylene carbonate, and then punched out in to a disk having adiameter of 0.5 cm to provide an electrolyte-impregnated porous sheethaving a thickness of about 50 μm. When the electrolyte-impregnatedporous sheet is measured for ion conductivity of in the same manner asin Example 16, it exhibits good ion conductivity of 4.6 mScm⁻¹.

Example 18

Using the same diblock copolymer comprising polyisoprene chain andpolymethyl methacrylate chain as used in Example 16, an electrolyteseparator for electrochemical cell is manufactured by melt extrusionmolding as described below.

A mixture of the diblock copolymer added with 2 wt % of a phenol-basedantioxidant (Sumilizer BP-76, Sumitomo Kagaku Kogyo Co., Ltd.) iskneaded at 180° C. to prepare pellets. The pellets are fed to anextruder and melt at 190° C., and then ejected from a sheet die having arectangular nozzle to manufacture a diblock copolymer sheet. The sheetis annealed under a nitrogen gas flow at 130° C. for 5 hours, and thenirradiated with an electron beam under the conditions of 2 MV inaccelerating voltage and 10 kGy in exposure dose. The sheet is rinsedwith a mixed solvent of MIBK and isopropyl alcohol (volume ratio: 3.7)to obtain a porous sheet.

The porous film is impregnated with a 1M solution of LiClO₄ (anhydride)in propylene carbonate, and the punched out into a disk having adiameter of 0.5 cm to provide an electrolyte-impregnated porous sheethaving a thickness of about 50 μm. When the electrolyte-impregnatedporous sheet is measured for ion conductivity in the same manner as inExample 16, it exhibits good ion conductivity of 4.1 mScm⁻¹.

Example 19

A hollow fiber filter is manufactured as follows.

A diblock copolymer (7) of polystyrene (PS) and polymethyl methacrylate(PMMA) (Mw=75,000, weight ratio of polystyrene unit=68%, Mw/Mn=1.03) isdissolved in propylene glycol methyl ether acetate (PGMEA) to prepare asolution. A hollow fiber made of polymethyl methacrylate is dip-coatedwith the solution. After being air-dried at 70° C., the hollow fiber isannealed under a nitrogen gas flow at 135° C. for 10 hours. Thereafter,the hollow fiber is irradiated with an electron beam under theconditions of 2 MV in accelerating voltage and 10 kGy in exposure dose.The hollow fiber is rinsed with a mixed solvent of MIBK and isopropylalcohol (volume ratio: 3.7) to provide a porous hollow fiber. Theresultant porous hollow fiber has an inner diameter of 500 μm and anouter diameter of 600 μm, and the side wall thereof is made porous towhich an OBDD type phase-separated structure of 35 nm in pore size istransferred.

Example 20

A hollow fiber filter is manufactured as follows.

A polymer blend of polystyrene (Mw=51,000, Mw/Mn=1.03) and polymethylmethacrylate (Mw=72,000, Mw/Mn=1.06) (weight ratio=6:4) is dissolved inPGMEA to prepare a solution. A hollow fiber made of polymethylmethacrylate is dip-coated with the solution. After being air-dried at70° C., the hollow fiber is annealed under a nitrogen gas flow at 135°C. for one hour to form a covering film having a thickness of 45 μm.Further, a solution of the diblock copolymer (7) of PS-PMMA in PGMEA,which is the same as that employed in Example 19, is prepared. The abovehollow fiber is dip-coated with the solution. The hollow fiber isair-dried to form a covering film having a thickness of 5 μm. The hollowfiber is annealed under a nitrogen gas flow at 135° C. for 10 hours.Thereafter, the hollow fiber is irradiated with an electron beam underthe conditions of 2 MV in accelerating voltage and 10 kGy in exposuredose. The hollow fiber is rinsed with a mixed solvent of MIBK andisopropyl alcohol (volume ratio: 3.7) to provide a porous hollow fiber.The resultant porous hollow fiber has an inner diameter of 500 μm and anouter diameter of 600 μm, and the side wall thereof has an asymmetricalfilm structure composed by an outer layer, to which an OBDD typephase-separated structure of 35 nm in pore size is transferred, and aporous inner layer having continuous pores of about 0.5 to 1 μm in poresize.

Example 21

A diblock copolymer of polystyrene (PS) and poly-tert-butyl acrylate(PtBA) is prepared. Then, 2 wt % of the diblock copolymer is dissolvedin PGMEA. Naphthylimidyl trifluoromethane sulfonate as a photo-acidgenerator is added to the solution at a ratio of 1.5 wt % based on thediblock copolymer. A glass substrate is spin-coated with the solution,and the dried on a hot plate at 110° C. for 3 minutes to form a filmhaving a thickness of 100 nm.

The glass substrate is set to a stepper, and then the diblock copolymerfilm is exposed with an i-line (365 nm). In the exposed portions, acidis generated from the naphthylimidyl trifluoromethane sulfonate, withwhich acid as a catalyst the tertiary butyl group of PtBA is decomposed,and hence the PtBA is turned into polyacrylic acid. The glass substrateis placed in an oven and subjected to annealing at 160° C. for one hour,thereby forming a structure having micro polymer phases in the film.

Next, RIE with CF₄ gas is performed. The microdomains of polyacrylicacid can be easily etched in the exposed portions, and further theunderlying glass substrate portion is also etched, but PS is leftunetched. In the unexposed portion, both PS and PtBA are left unetched.As a result, a pattern of holes having a diameter of about 90 nm can beformed only in the exposed portions.

Example 22

A diblock copolymer of polystyrene (PS) and polymethyl methacrylate(PMMA) is prepared. Then, 2 wt % of the diblock copolymer is dissolvedin PGMEA. A glass substrate is spin-coated with the solution and driedon a hot plate at 110° C. for 3 minutes to form a film having athickness of 100 nm. The glass substrate is placed in an oven andannealed in a nitrogen atmosphere at 210° C. for 10 minutes,subsequently at 135° C. for 10 hours, thereby forming a structure havingmicro polymer phases in the film.

The glass substrate is set to an electron beam irradiation apparatus(EX-8D, Toshiba Co., Ltd.) and the diblock copolymer film is exposed toan electron beam to cut the main chain of the PMMA. The film isdeveloped with a developer (a 3:7 mixed solution of MIBK and IPA) for anelectron beam resist. In the exposed portions, PMMA whose main chain iscut is etched, but PS is left unetched. In the unexposed portions, bothPS and PtBA are left unetched. Next, the glass substrate at portionsexposed to outside is etched with hydrofluoric acid for one minute usingthe pattern of remaining polymer as a mask. Thereafter, the substrate issubjected to an ultrasonic washing in acetone, thereby removing thepattern of remaining polymer. As a result, a pattern of holes having adiameter of about 90 nm can be formed only in the exposed portions.

Example 23

A film having micro polymer phases is formed on a 3-inch SiO substrateby annealing in a nitrogen gas atmosphere in the same manner asdescribed in Example 1 except that 0.1 wt %, based on the diblockcopolymer, of a phenol-based antioxidant (Sumilizer BP-101, SumitomoKagaku Kogyo Co., Ltd.) is added to a solution of the diblock copolymer(1).

When the annealed film having micro polymer phases is measured forinfrared absorption spectrum, chemical denaturing such as oxidationresulting from annealing is found suppressed in the film having micropolymer phases.

Thereafter, in the same manner as described in Example 1, the SiOsubstrate is etched using the film having micro polymer phases as amask. As a result, holes having a diameter of 12 nm and a depth of 18 nmcan be formed over the entire surface of the SiO substrate at a densityof about 2000/μm² and at approximately regular intervals. As comparedwith the holes of Example 1, the depth of holes formed in this exampleis deeper and dispersion of intervals between holes is reduced by half.

As described above, addition of an antioxidant can suppress theoxidative denaturing of the diblock copolymer resulting from annealing,making it possible to improve pattern-forming capability and etchingproperties of the diblock copolymer.

Further, even if annealing is performed in air atmosphere, it ispossible to form holes having a diameter of 12 nm and a depth of 18 nmover the entire surface of the SiO substrate at a density of about2000/μm² and at approximately regular intervals like the above case. Onthe other hand, in the case where a diblock copolymer containing noantioxidant is annealed in air atmosphere to form a film having micropolymer phases, the depth of holes formed in the substrate is as shallowas 10 nm and the intervals between holes are relatively uneven. Asdescribed above, when an antioxidant is added to a diblock copolymer, itis possible to form a good pattern even in air as that given undernitrogen gas flow.

Further, pattern formation is performed in the same manner as describedabove using a phosphorus-based antioxidant such as Sumilizer-P-16 andAdecastab PEP-24G; sulfur-based antioxidant such as Sumilizer-TPM andSumilizer-TP-D (all available from Sumitomo Kagaku Kogyo Co., Ltd.); andan HALS-type antioxidant such as Sanol LS-770 (Sankyo Co., Ltd.) inplace of the phenol-based antioxidant. Even when any of theseantioxidants is used, it is possible to increase the depth of the holesby about 20% and to suppress dispersion in intervals between the holesas compared with those obtained in Example 1 irrespective of whether theannealing atmosphere is nitrogen or air.

Example 24

A film having micro polymer phases is formed on a 3-inch SiO substrateand then, a pattern is formed in the same manner as described in Example2 except that 0.1 wt %, based on the diblock copolymer, of an ester typeantioxidant represented by the following chemical formula is added to asolution of the diblock copolymer (1) and that annealing is performed inair atmosphere. As a result, it is possible to obtain a good pattern asin the case of Example 2.

Further, pattern formation is performed in the same manner as describedabove using a phenol-based antioxidant such as Sumilizer-GA-80,Sumilizer-BP-101, Sumilizer-BP-76 (all available from Sumitomo KagakuKogyo Co., Ltd.), 3,5-di-tert-butyl-4-hydroxy toluene (BHT), aphosphorus-based antioxidant such as Sumilizer-P-16 and AdecastabPEP-24G, sulfur-based antioxidant such as Sumilizer-TPM andSumilizer-TP-D (all available from Sumitomo Kagaku Kogyo Co., Ltd.), andan HALS-type antioxidant such as Sanol LS-770 (Sankyo Co., Ltd.) inplace of the ester-type antioxidant. Even when any of these antioxidantsis used, it is possible to provide a good pattern as in the case ofExample 2.

Incidentally, when annealing is performed in air without adding anantioxidant, the size of holes and dispersion of intervals between holesin the formed pattern are increased. It is confirmed from these resultsthat the addition of an antioxidant to the diblock copolymer iseffective.

Example 25

A phenol-based antioxidant such as Sumilizer-GA-80, Sumilizer-BP-101 andSumilizer-BP-76 (all available from Sumitomo Kagaku Kogyo Co., Ltd.),BHT, the aforementioned ester type antioxidant, a phosphorus-basedantioxidant such as Sumilizer-P-16 and Adecastab PEP-24G, a sulfur-basedantioxidant such as Sumilizer-TPM and Sumilizer-TP-D (all available fromSumitomo Kagaku Kogyo Co., Ltd.), and an HALS-type antioxidant such asSanol LS-770 (Sankyo Co., Ltd.) are provided.

A pattern transfer step and patterning of SiO₂ film are performed in thesame manner as described in Example 5 except that 0.1 wt % of anantioxidant is added to polysilane constituting a pattern transfer filmand that annealing for forming a microphase separation is performed inair. As a result, even when any of these antioxidants is used, it ispossible to increase the depth of the holes by about 30% as comparedwith that obtained in Example 5.

Example 26

A phenol-based antioxidant such as Sumilizer-GA-80, Sumilizer-BP-101 andSumilizer-BP-76 (all available from Sumitomo Kagaku Kogyo Co., Ltd.),BHT, the aforementioned ester-type antioxidant, a phosphorus-basedantioxidant such as Sumilizer-P-16 and Adecastab PEP-24G, a sulfur-basedantioxidant such as Sumilizer-TPM and Sumilizer-TP-D (all from SumitomoKagaku Kogyo Co., Ltd.), and an HALS-type antioxidant such as SanolLS-770 (Sankyo Co., Ltd.) are provided.

Patterning is performed in the same manner as described in Example 13except that 0.1 wt % of an antioxidant is added to the diblock copolymerand that annealing for forming microphase separation is performed inair. As a result, even when any of these antioxidants is used, it ispossible to increase the depth of the holes formed in the SiO substrateby about 20% as compared with that obtained in Example 13.

Incidentally, when annealing is performed in air without adding anantioxidant, the size of holes and intervals between holes in the formedpattern are increased, and at the same time, the depth of holes isdecreased by about 20%. It is confirmed from these results that additionof an antioxidant to the diblock copolymer is effective.

Example 27

An example of manufacturing a field emission display (FED) as shown inFIG. 9 will be described. The cathode conductor 102 consisting of a thinfilm made of a metal such as niobium (Nb), molybdenum (Mo) or aluminum(Al) is formed on the insulative substrate 101 such as glass. A portionof the cathode conductor 102 is etched by means of photolithography toform a rectangular cut-out portion having a side length of about 40 to100 μm. The resistance layer 103 having a thickness of 0.5 to 2.0 μm isformed to cover the cathode conductor 102 by sputtering or CVD. As forthe material for the resistance layer 103, In₂O₃, Fe₂O₃, ZnO or NiCralloy or silicon doped with impurities can be employed. The resistivityof the resistance layer 103 should preferably be in the range of about1×10 to 1×10⁶ Ωcm.

The resistance layer 103 is patterned by wet etching with an alkalinesolution such as ammonia or reactive ion etching (RIE) with afluorine-based gas, thereby forming a plurality of terminals 103A. Then,the insulating layer 104 consisting of silicon dioxide and having athickness of about 1.0 μm is formed by sputtering or CVD to cover thecathode conductor 102 and the resistance layer 103. Further, the gateconductor 105 made of Nb or Mo having a thickness of 0.4 μm is formed bysputtering on the insulating layer 104.

Then, a resist (OFPR 800, 100pc, Tokyo Ohka Co., Ltd.) is patterned toprotect intersecting portions between gate wires and emitter wires.Subsequently, according to Example 6, a solution of the diblockcopolymer (5) and polystyrene homopolymer is applied to the gateconductor 105 by spin coating and then dried, followed by annealing,thereby forming a film having micro polymer phases. RIE with CF₄ gas isperformed to the film having micro polymer phases, thus the PMMA in thefilm having micro polymer phases is selectively etched, and further thegate conductor 105 is etched with using the pattern of remaining PS asmask, thereby transferring the pattern to the gate conductor 105.Thereafter, ashing is performed with an O₂ asher, thereby removing theremaining organic substances. In such a manner, many openings 106 havinga diameter of about 840 nm are formed in the gate conductor 105. Wetetching with a buffered hydrofluoric acid (BHF) or RIE with a gas suchas CHF₃ is performed to remove the insulating layer 104 in the openings106 until the resistance layer 103 is exposed to the outside.

Then, aluminum is obliquely deposited by electron beam (EB) evaporationto form a peeling layer. Molybdenum is normally deposited on the peelinglayer in the perpendicular direction by EB evaporation, therebydepositing molybdenum in a conical configuration inside the openings 106to form the emitters 107. Thereafter, the peeling layer is removed witha peeling solution such as phosphoric acid, thereby manufacturing an FEDdevice as shown in FIG. 9.

Example 28

An example of manufacturing an FED device as shown in FIG. 10 will bedescribed. The Pyrex glass substrate 201 having a width across corner of14 inches and a thickness of 5 mm is cleaned, and then the surfacethereof is roughened by plasma treatment. The emitter wires 202 having awidth of 350 μm are formed on the glass substrate 201 parallel to thelong side of the glass substrate 201 with a pitch of 450 μm. On thisoccasion, the regions on the substrate 201 having a width of 2 inchesmeasured from each side parallel to the direction of the emitter wires202 are made margins, respectively, for which patterning is performed sothat the emitter wires 202 are not formed in these regions.Specifically, patterning is performed in such a manner that a PVA filmis applied to the substrate, which is exposed to an ultraviolet raythrough a mask (photopolymerized), followed by being developed, so as toleave the PVA film in the regions between the emitter wires 202. Thepatterning precision at that time is 15 μm. A 50-nm thick Ni film isdeposited by electroless plating, and then the PVA film and the Ni filmthereon are lifted-off. A 1-μm thick Au film is deposited byelectroplating using the remaining Ni film as an electrode.

The SiO₂ film 203 having a thickness of 1 μm as an insulating film isdeposited by means of an LPD method. Even though a large number ofparticle defects are included in SiO₂ film 203, the density thereof isabout 1,000/cm², which is in a level that brings about no problem inpractical viewpoint. Although the film formed on the Au layer isslightly darkened, the film has a breakdown voltage of 100V per 1 μm,which is in a level that brings about no problem in practical viewpoint.The SiO₂ film 203 covers step portions of Au—Ni wire conformally, thusthere are no exposed portions of Au. A 30-nm thick Pd film is depositedon the SiO₂ film 203 by electroless plating, and then a 200-nm thick Irfilm is deposited by electroplating to form a gate film. Then, the gatefilm is patterned in the direction parallel to the shorter side of thesubstrate, thereby forming the gate wires 204 having a width of 110 μmwith a pitch of 150 μm. On this occasion, the regions on the substrate201 having a width of 2 inches measured from each side parallel to thedirection of the gate wires 204 are made margins, respectively, forwhich patterning is performed so that the gate wires 204 are not formedin these regions. Specifically, patterning is performed in such a manneras described above that a PVA film is applied to the substrate, which isexposed to an ultraviolet ray through a mask (photopolymerized),followed by being developed, so as to leave the PVA film on the gatewires 202 and remove the remaining exposed regions of the PVA film. Thepatterning precision at that time is also 15 μm.

Next, patterning is performed to remove a part of the gate wires 204 andSiO₂ film 203 until the emitter wire 202 is exposed to the outside,thereby forming the openings 205 in an approximately circular form.There are two reasons for separately performing the patterning of thegate wires 204 and the patterning of the SiO₂ film 203. One of thereasons is that, since the diameter of the openings 205 is about 1 μm,it is required to employ a patterning method ensuring optical resolutionof 1 μm or so. The other reason is that, since the openings 205 are notnecessarily arrayed regularly, it is only required that the openings 205having approximately uniform diameter are present in almost equalnumbers for respective pixels.

Specifically, patterning for the openings 205 is performed as follows. Adiblock copolymer (polystyrene: Mw=150,700, poly(t-butyl acrylate):Mw=1033,000, Mw/Mn=1.30) and polystyrene homopolymer (Mw=45,000,Mw/Mn=1.07) are blended together at a weight ratio of 21:79, and thenthe blend is dissolved in cyclohexane with 5 wt % of solid matters, towhich 1% of naphthylimide triflate, based on the solid matters, is addedas a photo-acid generator, followed by filtering. The solution isapplied to the gate wires 204 by spin coating, followed by drying at110° C., thereby forming a polymer film having a thickness of 970 nm.Excluding the intersecting portions between the gate wires 204 and theemitter wires 202, only the regions where the openings 205 are to beformed are exposed to g-line, thereby generating acid from thephoto-acid generator. The sample is placed in an oven and subjected toannealing in a nitrogen atmosphere at 150° C. for one hour, therebyforming a film having micro polymer phases, and, at the same time,decomposing exposed portions of poly(t-butyl acrylate) with acid toconvert into polyacrylic acid. Note that, since reflow of the polymeroccurs during annealing, the thickness of the polymer film on the gatewires 204 is decreased to 1 μm. The substrate is entirely immersed in analkaline solution for 3 minutes to remove the “island” portions of theacrylic acid, followed by rinsing with pure water, thus the gate wires204 are exposed to the outside. RIE is performed to etch the gate wires204 and further to etch the SiO₂ film 203 under the gate wires 204, thusthe emitter wires 202 are exposed to the outside.

Next, the resistance layer 206 is deposited inside the openings 205 byelectrophoresis. The operation is performed for separated regions eachincluding 100 lines of emitter wires, respectively. As a material forthe resistance layer 206, employed is a mixture of polyimide fineparticles having particle size of 100 nm (PI Technique Research Co.,Ltd.) and carbon fine particles containing fullerene having a particlesize of 10 nm at a weight ratio of 1000:1. The mixture is dispersed by0.4 wt % in a dispersion solvent (Isoper L, Exxon Chemical Co., Ltd.).On the other hand, zirconium naphthenate (Dai Nippon Ink Kagaku KogyoCo., Ltd.) as a metal salt is added by 10 wt % to the mixture ofpolyimide and carbon fine particles. The substrate 201 is immersed inthe dispersion solution and an counter electrode is disposed at a spaceof 100 μm away from the substrate 201, and the emitter wires 202 aregrounded, under which setting a voltage of +100V is applied to thecounter electrode while applying an ultrasonic wave. Immediately afterthe application of the voltage, a current of several mA begins to flow,but the current is exponentially attenuated, which comes to be notobserved two minutes later. At this moment, the resistance materialdispersed in the dispersion solvent is all deposited on the substrate201. Subsequently, the counter substrate is grounded and a voltage of+50V is applied to the gate wire 204, thereby migrating the fineparticles adhered on the gate wire 204 in the solvent so as to beremoved. Further, annealing is performed in a nitrogen gas atmosphere at300° C. to fix the resistance layer 206 to the emitter wires 202.

Then, a fine particle-emitter layer 207 is deposited on the resistancelayer 206 by electrophoresis in the same manner as described above. As amaterial for the fine particle-emitter layer 207, cubic boron nitridefine particles having a particle size of 100 nm (trade name SBN-B, ShowaDenko Co., Ltd.) are provided. The BN fine particles are treated withhydrofluoric acid, followed by hydrogen plasma treating at 450° C. TheBN fine particles are dispersed by 0.2 wt % in the same solvent asemployed in the deposition of the resistance layer. Further, zirconiumnaphthenate is added by 10 wt % to the BN fine particles. After the BNfine particles are deposited in the same manner as described above, theBN fine particles adhered on the gate wires 204 are removed. Further,annealing in a hydrogen atmosphere at 350° C., thereby fixing the fineparticle-emitter layer 207 to the resistance layer 206.

To the resultant electron-emitting element array, a faceplate 211provided with an anode layer 212 made of ITO and a phosphor layer 213 ismounted with interposing spacers 208 having a height of 4 mm, whichproduct is placed in a vacuum chamber. The pressure inside the vacuumchamber is reduced to 10⁻⁶ Torr by means of a turbo-molecular pump. Theanode potential is set to 3500V. The potentials of non-selected emitterwires 202 and gate wires 204 are both set to 0V. The potentials of aselected emitter wire 202 and a gate wire 204 are biased to −15V and+15V, respectively. As a result, electron emission is caused, and hencea bright spot is observed on the fluorescence layer 213. Several pixelsare selected from the entire displaying region of the display to measurefor brightness under the same conditions. As a result, dispersion of thebrightness is found to be within 3%.

Example 29

First, for the purpose of employing a porous film manufactured from ablock copolymer as a separator of a lithium ion secondary battery, apreliminary experiment is performed as follows.

A diblock copolymer comprising a polyvinylidene fluoride chain and apolymethyl methacrylate chain (weight average molecular weightMw=79,000, Mw/Mn=2.2, and weight fraction of polyvinylidenefluoride=66%) is dissolved in a solvent, to which silica (Tokuseal P,Tokuyama Soda Co., Ltd.) is added by 3 wt % based on the diblockcopolymer. The resultant solution is cast to provide a cast film of thediblock copolymer. The film is heat-treated under a nitrogen flow at130° C. for 5 hours to form a structure having micro polymer phasestherein. When the structure having micro polymer phases is observed withTEM, a bicontinuous structure having a pore size of 40 nm or so isformed. The cast film is irradiated with an electron beam under theconditions of 2 MV in accelerating voltage and 10 kGy in exposure dose,thereby decomposing the polymethyl methacrylate phase, and, at the sametime, cross-linking the polyvinylidene fluoride phase to cause gelation.The film is rinsed with ethyl acetate to remove the polymethacrylatephase. TEM observation shows that a porous film is formed havingcontinuous pores retaining the bicontinuous structure.

LiClO₄ anhydride is dissolved in a mixed solvent of propylene carbonateand dimethyl carbonate (1:1) to prepare a 1M concentration ofelectrolyte solution. The porous film having a thickness of about 50 μmobtained as above is impregnated with the electrolyte solution, and thefilm is punched out into a disk having a diameter of 0.5 cm. Theelectrolyte-impregnated porous film is sandwiched between a pair ofplatinum electrodes to constitute a cell, which is measured for ACimpedance using an impedance gain phase analyzer 1260 (SchlumbergerInstruments Co., Ltd.) at room temperature and at a frequency of 30 MHzto 0.05 Hz. As a result, the film exhibits good ion conductivity of 4mScm⁻¹ at 25° C. In addition, the porous film holds the electrolytesolution well, and hence, no liquid leakage occurs.

Next, a lithium ion secondary battery is manufactured as follows.

As an active material for a positive electrode, LiCoO₂ is employed. TheLiCoO₂ is heated under an argon atmosphere at 300° C. for 3 hours so asto be dried. Thereafter, LiCoO₂, conductive carbon black and the abovediblock copolymer are mixed together at a ratio of 85:10:5, to whichmixture a small quantity of DMF is added, and then kneaded. The kneadedproduct is uniformly applied to an aluminum mesh having a thickness of20 μm and a size of 4 cm×4.5 cm and dried to manufacture a positiveelectrode having a thickness of about 50 μm. The resultant positiveelectrode has LiCoO₂ weight per unit area of 17 mg/cm². The activematerial for positive electrode shows a capacity of 150 mAh/g.

As an active material for a negative electrode, hard carbon(non-graphitizing carbon) that is obtained by sintering furfuryl alcoholat 1,100° C. is employed. The hard carbon is heated under an argonatmosphere at 600° C. for 3 hours so as to be dried. The hard carbon,conductive carbon black and the above diblock copolymer are mixedtogether at a weight ratio of 85:10:5, to which mixture a small quantityof DMF is added, and then kneaded. The kneaded product is uniformlyapplied to a copper mesh having a thickness of 20 μm and a size of 4cm×4.5 cm and dried to manufacture a negative electrode having athickness of about 50 μm. The resultant positive electrode has hardcarbon weight per unit area of 7 mg/cm². The active material fornegative electrode shows a capacity of 150 mAh/g.

The aforementioned diblock copolymer is dissolved in a solvent, to whichsilica (Tokuseal P, Tokuyama Soda Co., Ltd.) is added 3 wt % based onthe diblock copolymer. The solution is cast to form a cast film of thediblock copolymer. The positive electrode, the negative electrode andthe cast film are respectively heat-treated under a nitrogen flow at130° C. for 5 hours, and then they are irradiated with electron beamunder the conditions of 2 MV in accelerating voltage and 10 kGy inexposure dose. The positive electrode, the cast film and the negativeelectrode are laminated in the order, followed by pressing with a hotpress, to manufacture a laminate. The laminate is rinsed with ethylacetate to remove the polymethacrylate phase in the diblock polymer. Thelaminate is heated under vacuum at 70° C. for 20 hours so as to bedried, thereby manufacturing a cell structure. LiPF₆ anhydride isdissolved in a mixed solvent of propylene carbonate and dimethylcarbonate (1:1) to prepare a 1M concentration of electrolyte solution.The cell structure is immersed in the electrolyte solution to beimpregnated with the electrolyte solution. The resultant cell structureis wrapped with waterproof and airtight aluminum laminate film andsealed under an argon flow. External electrode terminals are connectedthe negative and positive electrodes, respectively, therebymanufacturing a lithium ion secondary battery.

The resultant lithium ion secondary battery is charged with a constantcurrent of 50 μA/cm², and, after the battery voltage reaches 4.2V,charged with a constant voltage. The charging time is defined as thetime at which excessive capacity of 30% is charged relative to thecapacity of 300 mAh/g of the active material for the negative electrode.After completion charging, the battery is allowed to stand for 30minutes, and then the battery is discharged with a constant current of50 μA/cm² until the battery voltage decreases to 2.5V. After completionof discharging, the battery is allowed to stand for 30-minutes. Theabove procedures are defined as one cycle, and the charge-and-dischargecycles are repeated to examine the battery capacity per gram of theactive material (hard carbon) for the negative electrode (i.e., negativeelectrode-reduced capacity: mAh/g) and the charge-and-dischargeefficiency (%) (a ratio of discharge capacity to charge capacity), foreach cycle.

Even when the charge-and-discharge cycle test is repeated up to 500cycles, any substantial change is not recognized in acharge-and-discharge curve and the battery capable is maintained at 80%or more, showing excellent in charge-and-discharge characteristics.Further, no internal short-circuit occurs. A lithium ion secondarybattery manufactured in the same manner as described above except thatthe positive and negative electrodes and cast film are laminated,followed by hot-pressing, which laminate is irradiated with an electronbeam, also shows excellent characteristics similar to those describedabove.

Example 30

A diblock copolymer comprising a polyvinylidene fluoride chain and apolymethyl methacrylate chain (weight average molecular weightMw=79,000, Mw/Mn=2.2, and weight fraction of polyvinylidenefluoride=66%) is dissolved in a solvent to prepare a solution. Thesolution is applied to a fiber of polymethyl methacrylate by dipcoating, followed by being air-dried at 70° C., and further the fiber isheated and dried under a nitrogen flow at 135° C. for 10 hours, and thusa film is formed on the surface of the polymethyl methacrylate fiber.The surface of the fiber is irradiated with an electron beam under theconditions of 2 MV in accelerating voltage and 10 kGy in exposure dose,thereby decomposing the polymethacrylate phase, and, at the same time,cross-linking the polyvinylidene fluoride phase to cause gelation. Thefiber is rinsed with ethyl acetate to remove the polymethacrylate phase,thereby providing a porous hollow fiber. The resultant porous hollowfiber has an inner diameter of 500 μm and an outer diameter of 530 μm,and the side wall thereof has a porous structure retaining a Gyroid typephase-separated structure having a pore size of 40 nm.

A filter module having an effective length of 25 cm is manufacturedusing a hundred hollow fibers obtained, and the module is used forfiltration of a solution of silica sol having an average particle sizeof 100 nm. No silica sol is observed in the filtrate.

Example 31

Pellets of a diblock copolymer comprising a polyacrylic acid chain and apolymethyl methacrylate chain (weight average molecular weightMw=82,000, Mw/Mn=1.3, and weight fraction of polyacrylic acid=26%) areprepared with using an extruder. The pellets are fed into a uniaxialextruder and extrusion-molded into a fiber having a diameter of 50 μm. Aplain weave fabric is made using the fiber, and then the fabric isheat-treated under a nitrogen flow at 135° C. for 10 hours. Thereafter,the fabric is irradiated with an electron beam under the conditions of 2MV in accelerating voltage and 10 kGy in exposure dose, therebydecomposing the PMMA phase. The fabric is rinsed with a mixed solvent ofMIBK and isopropyl alcohol (volume ratio: 3.7) to remove the PMMA phase.Observation of the resultant fabric with SEM shows that the fabric isformed of an aggregate consisting of a bundle of ultrafine fibers madeof polyacrylic acid having a diameter of about 26 nm. It is assumed fromthe result that the annealed fiber is formed into a cylindricalstructure.

Example 32

A fabric is manufactured in the same manner as in Example 32 except thata diblock copolymer comprising a polyacrylic acid chain and a polymethylmethacrylate chain (weight average molecular weight Mw=104,000,Mw/Mn=1.3, and weight fraction of polyacrylic acid=55%) is employed.Observation of the fabric with SEM shows that the fabric is formed of anaggregate consisting of a bundle of fibers in a form of thin piece madeof polyacrylic acid having a thickness of 67 nm. It is assumed from theresult that the annealed fiber is formed into a lamella structure.

Example 33

A fabric is manufactured in the same manner as in Example 32 except thata diblock copolymer comprising a polyacrylic acid chain and a polymethylmethacrylate chain (weight average molecular weight Mw=42,000,Mw/Mn=1.3, and weight fraction of polyacrylic acid=65%) is employed.Observation of the fabric with TEM shows that the fabric is formed ofporous fibers made of polyacrylic acid including continuous pores havingan average pore size of 16 nm. It is assumed from the result that theannealed fiber is formed into a bicontinuous structure.

Example 34

A 2-wt % of diblock copolymer (molecular weight: polystyrene=65,000;polymethyl methacrylate=13,200; Mw/Mn=1.04) is dissolved inpropyleneglycol monoethyl ether acetate (PGMEA) to prepare a solution,followed by filtering, and then the solution is applied to a SiOsubstrate having a diameter of 3 inches by spin coating at a rate of2,500 rpm. The substrate is heated at 120° C. for 90 seconds toevaporate the solvent. Then the substrate is placed in an oven andsubjected to annealing in a nitrogen atmosphere at 210° C. for 10minutes, subsequently at 135° C. for 10 hours. As a result, formed is afilm having micro polymer phases of a sea-island structure includingislands having a diameter of 17 nm.

RIE is performed to the sample under the conditions of CF₄, 0.01 Torr,150 W of progressive wave, and 30 W of reflected wave. Under theconditions, the PMMA is selectively etched, and further the underlayeris etched with the remaining PS pattern being used as a mask. A 15-nmthick CoPtCr film is deposited by ordinary sputtering on the sample thathas been subjected to etching. The sample on which the CoPtCr film isdeposited is immersed in a cellosolve-based solvent and subjected toultrasonic cleaning, and thus the remaining polystyrene and the CoPtCrfilm thereon are lifted off. The surface of the sample after lift-offprocess is observed with a scanning electron microscope. As a result,observed is a structure that CoPtCr magnetic particles having a size ofabout 17 nm are present in the glass substrate matrix.

In order to use the sample as a high-density magnetic recording medium,carbon having a thickness of 10 nm is deposited as a protective film onthe substrate by sputtering, from which anomalous projections areremoved by tape vanishing, and then a lubricant is applied thereto in awet process. Measurement for the magnetic characteristics of the sampleshows perpendicular magnetic anisotropy with coercivity of 2 kOe.

Alternatively, a magnetic recording medium is manufactured in the samemanner as described above except that patterning of the diblockcopolymer is preformed according to the method in Example 2. As aresult, the resultant magnetic recording medium has almost the samecharacteristics as above.

Further, a magnetic recording medium is manufactured in the same manneras described above except that patterning of the diblock copolymer ispreformed according to the method in Example 4. Since the depth of holesformed by using the method is as deep as 30 nm, the resultant magneticrecording medium has higher coercivity than that of above magneticrecording medium.

Example 35

First, a diblock copolymer of polystyrene (molecular weight: 6,300) andpolymethyl methacrylate (molecular weight: 13,000) with Mw/Mn of 1.4 isdissolved in propyleneglycol monoethyl ether acetate (PGMEA) to preparea solution. The solution is applied in a thickness of about 10 nm to aglass substrate having a diameter of 2.5 inches by spin coating. Thecoated substrate is placed in a thermostat and subjected to annealing at150° C. for 24 hours, and further at 120° C. for 2 hours, and thereturned to room temperature. The surface of the glass substrate sampleafter annealing is observed with a scanning electron microscope. As aresult, it is confirmed that a structure in which spherical islandshaving an average diameter of 17 nm and the sea surrounding the islandsare phase-separated is formed.

Reactive ion etching (RIE) treatment with CF₄ is performed to thesample. As a result, only the island portions are selectively etched.Measurement for thickness of the film shows that the selectivity betweenthe island and sea to RIE is sea: island=1:4.

A 15-nm thick CoPtCr film is deposited by ordinary sputtering on thesample that has been subjected to etching. The sample on which theCoPtCr film is deposited is immersed in a cellosolve-based solvent andsubjected to ultrasonic cleaning, and thus the remaining polystyrene andthe CoPtCr film thereon are lifted off. The surface of the sample afterlift-off process is observed with a scanning electron microscope. As aresult, observed is a structure that CoPtCr magnetic particles having asize of about 15 nm are present in the glass substrate matrix.

In order to use the sample as a high-density magnetic recording medium,carbon having a thickness of 10 nm is deposited as a protective film onthe substrate by sputtering, from which anomalous projections areremoved by tape vanishing, and then a lubricant is applied thereto in awet process. Measurement for the magnetic characteristics of the sampleshows perpendicular magnetic anisotropy with coercivity of 2 kOe.

Example 36

An aluminum layer having a thickness of 500 nm is formed on a siliconwafer, and then the aluminum layer is patterned using a resist forsemiconductor (EOBR-800), thereby forming a pair of electrodes spacedapart from each other by 5 μm. A SiO₂ film is formed on the wafer, andthe surface thereof is flattened by CMP, thereby exposing the electrodeportions to the outside. An aluminum layer having a thickness of 20 nmis deposited on the wafer, and then a SiO layer having a thickness of 5nm is deposited on the aluminum layer. Patterning for forming electrodesis again performed using the resist for semiconductor (EOBR-800), andthen, RIE is slightly performed so as to expose the electrode portionsto the outside.

A diblock copolymer (molecular weight: polystyrene=146,700; polymethylmethacrylate=70,700; Mw/Mn=1.11) is dissolved in PGMEA to prepare a 2 wt% solution, which is applied to the wafer by spin coating at a rate of3,000 rpm, and then the wafer is placed on a hot plate heated at 120° C.to form a diblock polymer thin film having a thickness of 45 nm.

The thin film is annealed in a nitrogen atmosphere at 230° C., 40 hours,while applying a voltage of 10V between the electrodes. During theoperation, the diblock copolymer of polystyrene and polymethylmethacrylate causes microphase separation, resulting in a structure thatcylinder phases are oriented perpendicular to the electrodes. The waferis cooled to 80° C. over two hours, and further naturally cooled to roomtemperature.

The wafer is then subjected to reactive ion etching with CF₄ under theconditions of 0.01 Torr, 30 sccm, and 150 W of progressive wave for 180seconds. As a result, the PMMA phases are selectively etched, andfurther underlying aluminum is also etched. As a result, an electrode ina comb shape having intervals of about 50 nm is formed betweenelectrodes spaced apart from each other by 5 μm.

Example 37

Aluminum is deposited on a silicon wafer to form a thin film having athickness of 10 nm. A 10-wt % solution of a diblock copolymer (molecularweight: polystyrene=322,400; polymethyl methacrylate=142,000;Mw/mn=1.11) in toluene is applied to the wafer by spin coating at a rateof 3,000 rpm, and then the wafer is placed on a hot plate heated at 120°C. to form a diblock polymer thin film having a thickness of 500 nm. Thethin film is dried in vacuum at 60° C. over 14 days. Further, aluminumis deposited on the thin film of the diblock copolymer to form a thinfilm having a thickness of 10 nm.

The thin film is annealed in a nitrogen atmosphere at 210° C. for 40hours, while applying a voltage of 1V between a pair of aluminum layers.During the operation, the diblock copolymer of polystyrene andpolymethyl methacrylate causes microphase separation, resulting in astructure that cylinder phases are oriented perpendicular to theelectrodes. The wafer is cooled to 80° C. over two hours, and furthernaturally cooled to room temperature.

The wafer is then subjected to reactive ion etching with CF₄ under theconditions of 0.01 Torr, 30 sccm, and 150 W of progressive wave for 600seconds. As a result, the PMMA phases are selectively etched, andfurther underlying aluminum and the substrate are also etched. Ashingwith oxygen is performed to remove the remaining polymer. As a result,trenches having a diameter of 100 nm at maximum and a depth of 1 μm canbe provided in the substrate.

Example 38

A Pyrex glass substrate is cleaned, and then the surface thereof isroughened by plasma treatment. Gold is deposited on the glass substrateto form a thin film having a thickness of 100 nm. A 10-wt % solution ofa diblock copolymer comprising a polystyrene chain and a polymethylmethacrylate chain (weight average molecular weight Mw=37,000,Mw/Mn=1.3, and weight fraction of polymethyl methacrylate=26%) intoluene is applied to the substrate by spin coating, and then thesubstrate is placed on a hot plate heated to dry at 120° C. to form adiblock polymer thin film having a thickness of 500 nm. The thin film isdried in vacuum at 60° C. over 14 days. Further, aluminum is depositedon the thin film of the diblock copolymer to form a thin film having athickness of 50 nm.

The thin film is annealed in a nitrogen atmosphere at 210° C. for 40hours, while applying a voltage of 1V between the gold film and thealuminum film. During the operation, the diblock copolymer ofpolystyrene and polymethyl methacrylate causes microphase separation,resulting in a structure that cylinder phases are oriented perpendicularto the electrodes. The substrate is cooled to 80° C. over two hours, andfurther naturally cooled to room temperature.

Then, the aluminum deposited film formed on the surface is removed byimmersing the substrate in an aqueous solution of hydrochloric acid, andthen the substrate is irradiated with an electron beam. After electronbeam irradiation, the cast film is rinsed with a mixed solution of MIBKand IPA in 3:7 by volume ratio, thereby making the polymer film porous.Observation of the porous polymer film with an electron microscope showsthat holes, which reach the gold film, having a diameter of 10 nm areformed perpendicular to the substrate. The porous film is subjected topotentiostatic electrolysis in a gold plating bath to deposit gold inthe through-holes. When the porous polymer layer is removed by ashingwith oxygen after electroforming, provided is a structure in which manygold fibers having a diameter of about 8 nm are arranged on the goldfilm with perpendicularly oriented to the substrate like a pinholder.Likewise, when iridium is subjected to electroforming, it is possible toprovide a pinholder structure similar to that in the case of gold.

Then, the field emission ability of the pinholder structure is examined.By making use of the gold film bearing the pinholder structure ofiridium having a diameter of 8 nm as a cathode electrode, and by makinguse of an ITO substrate on which red-emitting europium-doped Al₂O₃phosphor as a counter anode electrode, a cell having a space betweenelectrodes of 30 μm is manufactured. The cell is actuated at a voltageof 300V in vacuum (1×10⁻⁶ Torr). As a result, it is observed redemission due to effective field emission, which shows that the pinholderstructure is capable of operating as emitters of a cold emissiondisplay.

Further, an FED panel is manufactured by making use of the emitter inthe pinholder structure. In this case, the FED panel is manufactured bythe same procedures as described in Example 27 except that, instead offorming a Spindt type emitter on an insulating layer by EB evaporation,the pinholder structure of iridium is formed as described above. To theresultant electron emission element array, a face plate provided with ananode layer made of ITO and with a phosphor layer is mounted throughspacers having a height of 4 mm, in the same manner as described inExample 28, and then the circumferential portions of the panel is sealedleaving a discharge port for evacuation. The pressure inside the elementpanel is reduced with a turbo-molecular pump to 10⁻⁶ Torr, and then thedischarge port is completely sealed to manufacture the FED panel. Inorder to operate the FED panel, the anode potential is set to 3500V, thepotentials of non-selected emitter wires and gate wires are both set to0V, and the potentials of selected emitter wire and gate wire are biasedto −15V and +15V, respectively. As a result, electron emission iscaused, and hence a bright spot is observed on the fluorescence layer.Several pixels are selected from the entire displaying region of thedisplay to measure for brightness under the same conditions. As aresult, dispersion of the brightness is found to be within 3%.

Example 39

Gold is deposited on a copper foil to form a thin film having athickness of 100 nm. A 10-wt % solution of a diblock copolymercomprising a polystyrene chain and a polymethyl methacrylate chain(weight-average molecular weight Mw=370,000, Mw/Mn=1.2, and weightfraction of polymethyl methacrylate chain=26%) in toluene is cast andair-dried and further drying is performed in vacuum at 60° C. for 8hours to form a diblock polymer film having a thickness of 30 nm.Aluminum is deposited on the cast film to form a film having a thicknessof 50 nm.

Annealing is performed in a nitrogen atmosphere at 210° C. for 40 hours,while applying a voltage of 60V between the gold film and the aluminumfilm. During the operation, microphase separation of the diblockcopolymer of the polystyrene and polymethyl methacrylate is caused, andcylinder phases of polymethyl methacrylate are oriented perpendicular tothe electrodes. The sample is cooled to 80° C. over two hours, and thennaturally cooled to room temperature.

Thereafter, the aluminum deposition film formed on the surface isremoved by immersing the sample in an aqueous solution of hydrochloricacid, and then the sample is irradiated with an electron beam. After theelectron beam irradiation, the cast film is rinsed in a 3:7 mixedsolution of MIBK and IPA to make the polymer film porous. When theporous polymer film is observed with an electron microscope, it is foundthat holes having a diameter of 120 nm, which reach the gold film, areformed perpendicular to the substrate. The porous film is subjected topotentiostatic electrolysis in a nitrogen-purged Bi³⁺/HTeO²⁺ bath usinga platinum mesh as a counter electrode, thereby depositing bismuthtelluride in the through-holes. When the porous polymer layer is removedafter the electroforming, it is possible to obtain a structure in whichmany bismuth telluride fibers having a diameter similar to that of thecylinder and oriented perpendicular to the substrate are formed on thegold film like a pinholder. The bismuth telluride fiber can be employedfor a high-efficiency thermoelectric conversion element.

Example 40

A solution of a diblock copolymer comprising a polystyrene chain and apolymethyl methacrylate chain (weight-average molecular weightMw=82,000, Mw/Mn=1.3, and weight fraction of polystyrene chain=26%) isapplied to an aluminum wire by dip coating. After application, the wireis air-dried. After drying, aluminum is deposited on the surface ofcoating by a thickness of 100 nm. After deposition, annealing isperformed in a nitrogen atmosphere at 200° C. for 40 hours, whileapplying a voltage of 30V between the aluminum wire and the aluminumdeposited film. During the annealing, microphase separation of thediblock copolymer of the polystyrene and polymethyl methacrylate iscaused, and cylinder phases are oriented perpendicular to theelectrodes. The wire is cooled to 80° C. over two hours, and thennaturally cooled to room temperature. After the heat treatment, the wireis immersed in an aqueous solution of hydrochloric acid to remove thealuminum deposited film formed on the surface of the wire. After thesurface aluminum deposited film is removed, the wire is irradiated withan electron beam at a dose of 150 KGr. After the electron beamirradiation, the cast film is rinsed in the mixed solution of MIBK andIPA in the ratio of 3:7 by volume to make the polymer film porous. Thewire is immersed in an aqueous solution of hydrochloric acid to dissolveand remove the aluminum wire forming the core, and thus a hollow fiberfilter is provided. The resultant hollow fiber has an inner diameter of500 μm and an outer diameter of 530 μm, whose wall surface represents aporous structure to which a cylinder type phase-separated structurehaving a pore size of about 27 nm is transferred. The cylindrical finepores are formed into through-holes oriented perpendicular to the wallsurface, which shows a suitable form for a filter.

When a minimodule (effective length: 25 cm) using 100 hollow fiberfilters is manufactured, the module works well as a filter apparatus.

Example 41

A diblock copolymer comprising a polyacrylic acid chain and a polymethylmethacrylate chain (weight-average molecular weight Mw=82,000,Mw/Mn=1.3, and weight fraction of polyacrylic acid chain=26%) ispalletized with an extruder, and then the pellets are extruded through aT-die to form a film having a thickness of about 100 μm. The film isheat-treated under a nitrogen gas flow at 135° C. for 10 hours. Afterthe heat treatment, the film is irradiated with an electron beam at thedose of 150 kGy. After the electron beam irradiation, the film is rinsedin the mixed solution of MIBK and IPA in the ratio of 3:7 by volume. SEMand TEM observation shows that formed is a flat material like anon-woven fabric in which fiber bundles of ultra fine fiber having athickness of 26 nm are entangled. The flat material shows excellentflexibility and can also be used well as a high-precision filter.

Example 42

A diblock copolymer of 1,2-polybutadiene and polymethyl methacrylate(Mw=281,000, weight fraction of 1,2-polybutadiene=32%, Mw/Mn=1.05) ismixed with a 2-wt % of 3,3′,4,4′-tetra(t-butylperoxycarbonyl)benzophenone, and a cyclohexanone solution thereof is prepared. Thesolution is applied to a glass plate using an applicator to form a sheethaving a thickness of 20 μm. The sheet is subjected to heat treatmentunder a nitrogen gas flow at 135° C. for two hours. The sheet isirradiated with an electron beam under the conditions of 2 MV inaccelerating voltage and 200 kGy in exposure dose. The sheet is rinsedwith ethyl lactate for 24 hours, and then rinsed with methanol for onehour to provide a porous sheet. The resultant porous sheet has a porousstructure to which transferred is a bicontinuous phase-separatedstructure consisting of polybutadiene cylinder phases having a diameterof about 50 nm and highly branched in a three-dimensional networkconfiguration.

The resultant porous sheet is subjected to repeating processescomprising steps of being impregnated with a poly(2-bromoethyl)silsesquioxane, being irradiated with an ultraviolet ray, and beingheat-treated at 80° C., by five times, and thuspoly(2-bromoethyl)silsesquioxane is sufficiently loaded into pores ofthe porous sheet. The porous sheet is subjected to heat-treatment in anitrogen gas flow at 150° C. for one hour and at 450° C. for one hour.As a result, manufactured is a silica porous body having a nanostructurethat is transferred using the porous structure of the porous sheet as atemplate.

A mixed solution of acrylonitrile mixed with 10 wt % of3,3′,4,4′-tetra(t-butylperoxycarbonyl) benzophenone is prepared. Thesilica porous body is impregnated with the solution. The silica porousbody is irradiated with an ultraviolet ray, thereby polymerizing andcuring the acrylonitrile. The structure is heated in air at 210° C. for24 hours, and then heated in a nitrogen gas flow from 210° C. to 800° C.at a rate of temperature rise of 10° C. per minute so as to becarbonized. The composite of silica and carbon is treated withhydrofluoric acid to solve out the silica. As a result, it is possibleto manufacture porous carbon having continuous pores reflecting themorphology of the 1,2-polybutadiene porous sheet.

Example 43

Synthesis of Diblock Copolymer:

In this example, a diblock copolymer consisting of polycyclohexadienederivative polymer chain(poly(cis-5,6-bis(pivaloyloxy)-2-cyclohexen-1,4-ylene)) and polyethyleneoxide (PEO) chain is synthesized by anion polymerization.

N-butyl lithium is employed as a reaction initiator. Employed ethyleneoxide is dried by passing through the column of calcium hydride, andthen, is distilled after a small amount of n-butyl lithium is added.Tetrahydrofuran (THF) used as a solvent is distilled twice usingmetallic sodium as a desiccating agent under an argon gas flow. As apolymerization apparatus, a pressure reactor (Taiatsu Glass Co., Ltd.)is employed. The reaction is carefully performed in argon atmosphereunder a pressure of 4 atm so as to prevent an external air from enteringthe interior of the reaction system.

Poly(cis-5,6-bis(pivaloyloxy)-2-cyclohexen-1,4-ylene is charged into thereactor, and then THF is introduced into the reactor immediately afterit is distilled. After the interior of the reactor is made into an argongas atmosphere, a solution of n-butyl lithium in heptane is introducedinto the reactor at −80° C., and then the mixture is stirred for oneweek. Subsequently, a predetermined quantity of ethylene oxide isintroduced into the reactor, and the mixture is further stirred. After 2mL of 2-propanol containing a small amount of hydrochloric acid is addedto the mixture to terminate the reaction, the reactor is opened. Afterthe reaction solution is concentrated by three-times, the reactionsolution is dropped in a sufficient amount of petroleum ether, therebyallowing a polymer to reprecipitate. After the polymer is separated byfiltration, the polymer is dried in vacuum at room temperature, therebyproviding a diblock copolymer.

The poly(cis-5,6-bis(pivaloyloxy)-2-cyclohexen-1,4-ylene) unit has Mw of65,000, the polyethylene oxide unit has Mw of 13,200, and Mw/Mn is 1.5.

Pattern Formation:

A mixture of the resultant diblock copolymer mixed with 5 wt % of3,3′,4,4′-tetrakis(t-butylperoxy-carbonyl)benzophenone is dissolved inmethylene chloride at a concentration of 2 wt %, followed by filtering,and then the solution is applied to a quartz glass substrate having adiameter of 3 inches by spin coating at a rate of 2,500 rpm to form apattern forming film. The substrate is heated at 110° C. for 90 secondsto evaporate the solvent. Thereafter, the substrate is placed in an ovenand then heat-treated in a nitrogen atmosphere at 150° C. for 5 hours,at 200° C. for 5 hours, at 300° C. for 5 hours and at 350° C. for 30minutes. When the surface of the substrate after heat-treatment isobserved with AFM, it is found that holes having a diameter of 12 nm areformed over the entire surface of the pattern forming film.

Reactive ion etching is performed under the conditions of CF₄, 0.01Torr, 150 W of progressive wave, and 30 W of reflected wave to etch thesubstrate. Thereafter, reactive ion etching is performed under theconditions of O₂, 0.01 Torr, 150 W of progressive wave, and 30 W ofreflected wave to remove the residue of the pattern forming film. Underthe conditions, only the organic substances can be efficiently ashed. Asa result, holes having a diameter of 12 nm and a depth of 25 nm areformed over the entire surface of the quartz substrate at a density ofabout 2000/μm² and at approximately equal intervals.

A CoPtCr thin film having a thickness of 15 nm is deposited over theentire surface of the quartz substrate by sputtering. Carbon having athickness of 10 nm is deposited as a protective film on the CoPtCr thinfilm by sputtering, from which anomalous projections are removed by tapevanishing, and then a lubricant is applied thereto to manufacture ahigh-density magnetic recording medium. The medium has perpendicularmagnetic anisotropy of 2 kOe.

Example 44

Synthesis of Diblock Copolymer:

In this example, a diblock copolymer consisting of polybutylmethylsilanechain and polyethylene oxide chain is synthesized by living anionpolymerization.

A masked disilene represented by the following chemical formula andethylene oxide are employed as monomers and sec-butyl lithium isemployed as a polymerization initiator, and these monomers aresuccessively introduced into in THF at a reaction temperature of −78° C.to synthesize the diblock copolymer. The weight-average molecularweights of respective blocks constituting the diblock copolymer are65,000 for polybutylmethylsilane and 13,200 for polyethylene oxide. Inaddition, molecular weight distribution (Mw/Mn) is 1.1.

Pattern Formation:

A 3-inch silicon wafer is spin-coated with a solution of polyamic acid(that is prepared by diluting Semicofine SP-341 available from TorayCo., Ltd. with N-methyl-2-pyrrolidone). Thereafter, the sample is heatedunder a nitrogen gas flow successively at 150° C., at 250° C. and at350° C., for one hour, respectively, thereby forming a pattern transferfilm consisting of polyimide having a thickness of 30 nm.

The synthesized diblock copolymer is dissolved in THF at a concentrationof 2 wt %, followed by filtering, and then the solution is applied tothe pattern transfer film made of polyimide by spin coating at a rate of2500 rpm, thereby forming a pattern forming film. The sample is heatedat 110° C. for 90 seconds to evaporate the solvent. Thereafter, thesample is placed in an oven and is heat-treated in a nitrogen atmosphereat 150° C. for 5 hours. Then, the sample is irradiated with anultraviolet ray from a low-pressure mercury lamp in air. The sample isplaced again in the oven and is heat-treated in a nitrogen atmosphere at150° C. for one hour, at 200° C. for 5 hours, at 300° C. for 5 hours,and at 350° C. for 30 minutes. When the surface of the substrate isobserved with AFM, it is found that holes having a diameter of about 13nm are formed over the entire surface of the pattern forming film.

Reactive ion etching is performed to the sample under the conditions ofO₂, 0.01 Torr, 150 W of progressive wave, and 30 W of reflected wave. Asa result, holes having relatively high aspect ratio of a diameter of 13nm and a depth of 30 nm are formed over the entire surface of polyimidefilm (a pattern transfer film) on the silicon wafer at a density ofabout 2000/μm² and at approximately equal intervals. RIE is performedunder the conditions of CF₄, 0.01 Torr, 150 W of progressive wave, and30 W of reflected wave using the polyimide porous film as an etchingmask to etch the silicon wafer. Subsequently, ashing is performed underthe conditions of O₂, 0.01 Torr, 150 W of progressive wave, and 30 W ofreflected wave to etch the remaining polyimide film. As a result, holesof having a high aspect ratio of a diameter of 14 nm and a depth of 70nm are formed over the entire surface of the silicon wafer at a densityof about 2000/μm² and at approximately equal intervals.

From the results described above, it is found that a porous mask can beformed from a diblock copolymer consisting of a polybutylmethylsilanechain and a polyethylene oxide chain, and that a dot pattern having ahigh aspect ratio can be formed in the polyimide film as a patterntransfer film, and further that the underlying substrate can bepreferably processed.

Example 45

Synthesis of Diblock Copolymer:

In this example, a diblock polymer (PEO-b-PDMSO) consisting of apolyethylene oxide (PEO) chain and a polydimethylsiloxane (PDMSO) chainis synthesized by living anion polymerization.

Using a polyethylene oxide macromer as a reaction initiator,hexamethylcyclotrisiloxane is polymerized. Tetrahydrofuran (THF) used asa solvent is distilled twice using metallic sodium as a desiccatingagent under an argon gas flow. The polyethylene oxide has an OH group atone terminal and is capped with methoxy group at the other terminal,which is freeze-dried from a solution in benzene immediately before use.As for the polymerization apparatus, a pressure reactor (Taiatsu GlassCo., Ltd.) is employed. The reaction is carefully performed in an argonatmosphere under pressure of 4 atm so as to prevent an external air fromentering the interior of the reaction system.

While flowing an argon gas, a solution of polyethylene oxide dissolvedin dehydrated benzene is introduced into the reactor, and the solutionis freeze-dried in vacuum over 5 hours. Under vacuum, THF is distilledand directly introduced into the reactor. The interior of the reactor isfilled with an argon gas atmosphere again, to which n-butyl lithium isadded at 0° C., followed by stirring at 30° C. for one hour, and thenhexamethylcyclotrisiloxane is added at 25° C. to the solution withstirring so as to be polymerized. A small amount of the reactionsolution is taken out to measure the molecular weight by GPC. Based onthe measured molecular weight, an amount of hexamethylcyclotrisiloxaneto be added to give a desired molecular weight is calculated and addedso to the solution. A series of these procedures are carefully performedunder a pressurized argon atmosphere so as to prevent an external airfrom entering the interior of the reaction system. After it is confirmedby GPC that a desired molecular weight is given, trimethylchlorosilaneis added to the solution to terminate the reaction, and then the reactoris opened. The reaction solution is concentrated by three-times, andthen the solution is dropped in a sufficient amount of petroleum etherto reprecipitate the polymer. The polymer is separated by filtration andthen is dried in vacuum at room temperature, thus the diblock copolymeris provided.

The polyethylene oxide has Mw of 65,000, the polydimethyl siloxane hasMw of 62,000, and Mw/Mn is 1.20.

Pattern Formation:

A 3-inch silicon wafer is spin-coated with a solution of polyamic acid(that is prepared by diluting Semicofine SP-341 available from TorayCo., Ltd. with N-methyl-2-pyrrolidone (NMP)). The sample is heated undera nitrogen gas flow successively at 150° C., at 250° C. and at 350° C.,for one hour, respectively, thereby forming a pattern transfer filmconsisting of polyimide having a thickness of 30 nm.

A mixture prepared by mixing the synthesized diblock copolymer with1,3,5,7,9,11,13-heptacyclopentyl-15-vinylpentacyclo[9.5.1.1^(3,9).1^(5,15).1^(7,13)] octasiloxane (Vinyl-POSS) andazobisisobutyronitrile in a weight ratio of 1:1:0.05 is dissolved in THFat a concentration of 2-wt %, followed by filtering. The solution isapplied to the pattern transfer film made of polyimide by spin coatingat a rate of 2500 rpm, thereby forming a pattern-forming film. Thesample is heated at 60° C. for 90 seconds to evaporate the solvent. Thesample is heat-treated a nitrogen atmosphere at 80° C. for 5 hours.Thereafter, the pattern-forming film is exposed to hydrochloric acidvapor. Then, the sample is heat-treated in a nitrogen atmosphere at 200°C. for one hour, at 250° C. for one hour, at 300° C. for one hour, andat 350° C. for 30 minutes. When the surface of the sample is observedwith AFM, it is found that holes having a diameter of about 15 nm areformed over the entire surface of the pattern forming film.

Reactive ion etching is performed to the sample under the conditions ofO₂, 0.01 Torr, 150 W of progressive wave, and 30 W of reflected wave. Asa result, holes having a relatively high aspect ratio of a diameter of15 nm and a depth of 30 nm are formed over the entire surface ofpolyimide film (a pattern transfer film) on the silicon wafer atapproximately equal intervals. RIE is performed using the polyimideporous film as a mask under the conditions of CF₄, 0.01 Torr, 150 W ofprogressive wave, and 30 W of reflected wave to etch the silicon wafer.Subsequently, ashing is performed under the conditions of O₂, 0.01 Torr,150 W of progressive wave, and 30 W of reflected wave to remove theremaining polyimide film. As a result, holes having a high aspect ratioof a diameter of 14 nm and a depth of 70 nm are formed over the entiresurface of the silicon wafer at approximately equal intervals.

Example 46

Pattern Formation:

A mixture of the diblock copolymer comprising polyethylene oxide andpolydimethylsiloxane synthesized in Example 45 and polyamic acidsynthesized from biphenyltetracarboxylic acid dianhydride andp-phenylene diamine in a weight ratio of 1:1 is dissolved in THF at aconcentration of 2 wt %, followed by filtering. The solution is appliedto a 3-inch silicon wafer by spin coating at a rate of 2500 rpm to forma pattern forming film. The sample is heated at 60° C. for 90 seconds toevaporate the solvent, and then is heat-treated in a nitrogen atmosphereat 8° C. for 5 hours. Thereafter, the pattern-forming film is exposed tohydrochloric acid vapor. Then, the sample is heat-treated in a nitrogenatmosphere at 200° C. for one hour, at 250° C. for one hour, at 300° C.for one hour, and at 350° C. for 30 minutes. When the surface of thesample is observed with AFM, it is found that holes having a diameter of15 nm are formed over the entire surface of the pattern forming film.

RIE is performed using the porous film as an etching mask under theconditions of CF₄, 0.01 Torr, 150 W of progressive wave, and 30 W ofreflected wave to etch the silicon wafer. Thereafter, ashing of theremaining polymer is performed under the conditions of O₂, 0.01 Torr,150 W of progressive wave, and 30 W of reflected wave. As a result,holes having a diameter of 14 nm and a depth of 5 nm are formed over theentire surface of the silicon wafer at approximately equal intervals.

Example 47

Synthesis of Diblock Copolymer:

In this example, a triblock copolymer (PAN-PEO-PAN) consisting ofpolyethylene oxide (PEO) chain and polyacrylonitrile (PAN) chains issynthesized by living anion polymerization. Using a polyethylene oxidemacromer (disodium salt of polyethylene oxide) as a reaction initiator,acrylonitrile is polymerized. Tetrahydrofuran and benzene used assolvents are distilled twice using lithium aluminum hydride as adesiccating agent under an argon gas flow, to which molecular sieves 4Ais charged. The acrylonitrile employed as a monomer is washedsuccessively with a saturated aqueous solution of NaHSO₃, a saturatedaqueous solution of NaCl containing 1% of NaOH, and a saturated aqueoussolution of NaCl, and then vacuum-distilled using calcium chloride as adesiccating agent, and further vacuum-distilled using calcium hydride asa desiccating agent under an argon gas flow, to which molecular sieves4A is charged. Sodium naphthalene is prepared by reacting naphthalenewith metallic sodium in THF. Crown ether (dicyclohexyl-18-crown-6) isfreeze-dried from a solution in benzene, and then is dissolved inbenzene. Polyethylene oxide, which has OH groups at both ends, isfreeze-dried from a solution in benzene immediately before use. As forthe polymerization apparatus, a pressure reactor (Taiatsu Glass Co.,Ltd.) is employed. The reaction is carefully performed in an argonatmosphere under pressure of 4 atm so as to prevent an external air fromentering the interior of the reaction system.

A solution of polyethylene oxide dissolved in dehydrated benzene isintroduced into the reactor with flowing an argon gas, and isfreeze-dried in vacuum over 5 hours. THF distilled under vacuum isdirectly introduced into the reactor. After the interior of the reactoris made into an argon gas atmosphere again, sodium naphthalene isintroduced into the reactor at 0° C., and further a solution of crownether in benzene is introduced at 30° C. with stirring. After themixture is stirred for one hour, acrylonitrile is added to the mixtureat −78° C. and allowed to polymerize with stirring. A small amount ofreaction solution is taken out to measure the molecular weight thereofby GPC. Based on the measured molecular weight, an amount ofacrylonitrile to be added to give a desired molecular weight iscalculated and added so to the solution. A series of these proceduresare carefully performed under a pressurized argon atmosphere so as toprevent an external air from entering the interior of the reactionsystem. After it is confirmed by GPC that a desired molecular weight isgiven, 2 mL of 2-propanol is added to the solution to terminate thereaction, and then the reactor is opened. The reaction solution isconcentrated by three-times and then is dropped in a sufficient amountof petroleum ether to reprecipitate a polymer. After the polymer isseparated by filtration, the polymer is vacuum-dried at roomtemperature, thus the triblock copolymer is provided.

The polyacrylonitrile has Mw of 65,000, the polyethylene oxide has Mw of13,200, and Mw/Mn is 1.40.

Pattern Formation:

A 2-wt % solution of resultant PAN-PEO-PAN triblock copolymer isfiltered, and then the solution is applied to a 3-inch quartz glasssubstrate by spin coating at a rate of 2,500 rpm to form a patternforming film. The sample is heated at 110° C. for 90 seconds toevaporate the solvent. Thereafter, the sample is placed in an oven andis heat-treated in a nitrogen atmosphere at 200° C. for 10 minutes,subsequently at 135° C. for 10 hours. The heat treatment at 200° C.flattens the film and can eliminate the histeresis after thespin-coating. In addition, the heat treatment at 135° C. can efficientlyadvance microphase separation. The sample is heat-treated in air at 200°C. for 24 hours, and then is heat-treated in a nitrogen atmosphere at350° C. for 30 minutes. When the surface of the substrate after the heattreatments is observed with AFM, it is found that holes having adiameter of about 12 nm are formed over the entire surface of thepattern forming film.

Reactive ion etching is performed to the sample under the conditions ofCF₄, 0.01 Torr, 150 W of progressive wave, and 30 W of reflected wave toetch the substrate. Thereafter, reactive ion etching is performed underthe conditions of O₂, 0.01 Torr, 150 W of progressive wave, and 30 W ofreflected wave to remove the residue of the pattern forming film.

As a result, holes having a diameter of 12 nm and a depth of 20 nm areformed over the entire surface of quartz glass substrate at a density ofabout 2000/μm² and at approximately equal intervals. The substrate canbe used as a substrate for a hard disk.

Example 48

Ten wt % of dioctyl phthalate is added as a plasticizer to thePAN-PEO-PAN triblock copolymer synthesized in Example 47. Heat-treatmentconditions for forming microphase separation of the block copolymer isset to: under a nitrogen gas flow at 200° C. for 10 minutes,subsequently at 135° C. for one hour, in air at 200° C. for 24 hours,and then under a nitrogen gas flow at 350° C. for 30 minutes. A filmhaving micro polymer phases is formed in a similar manner to that inExample 47 except for these conditions. The sample is etched using thefilm having micro polymer phases as a mask. As a result, a patternsimilar to that in Example 47 can be formed in the substrate. Asdescribed above, addition of the plasticizer can shorten theheat-treating time.

Example 49

A 2-wt % solution of PAN-PEO-PAN triblock copolymer synthesized inExample 47 is filtered, and then the solution is applied to a 3-inchquartz glass substrate by spin coating at a rate of 2,500 rpm to form apattern forming film. The sample is heated at 110° C. for 90 seconds toevaporate the solvent. The sample is placed in an oven and isheat-treated in a nitrogen atmosphere at 200° C. for 10 minutes and at135° C. for 10 hours. The sample is heat-treated in air for 24 hours at200° C., and then is heat-treated in a nitrogen atmosphere at 350° C.for 30 minutes. Next, the substrate is etched with hydrofluoric acid forone minute. Thereafter, ultrasonic washing is performed in acetone toremove the remaining polymer.

As a result, holes having a diameter of 15 nm and a depth of 12 nm areformed over the entire surface of quartz glass substrate at a density ofabout 2000/μm² and at approximately equal intervals. In such a manner,the substrate can be patterned with only wet etching without using a dryetching process. The substrate can be used as a substrate for a harddisk.

Example 50

Synthesis of Diblock Copolymer:

Using polyethylene oxide having a methoxy group at one terminal andhaving an OH group at the other terminal, a diblock polymer (PAN-b-PEO)consisting of a polyethylene oxide (PEO) chain and a polyacrylonitrile(PAN) chain is synthesized by living anion polymerization by a similarmethod to that in Example 47. The polyacrylonitrile has Mw of 10,600,the polyethylene oxide has Mw of 35,800, and Mw/Mn is 1.37.

Pattern Formation:

A CoPtCr magnetic film is formed on a quartz glass substrate. A patternforming film made of the above diblock copolymer is formed on themagnetic film, and then the pattern forming film is allowed to form astructure having micro polymer phases. Thereafter, the CoPtCr magneticfilm is subjected to wet etching in a similar manner to that in Example49. As a result, formed is a magnetic film structure in whichprojections having a diameter of 15 nm and a height of 12 nm are formedover the entire surface of quartz glass substrate at a density of about1800/μm² and at approximately equal intervals.

Example 51

A quartz substrate is spin-coated with a solution of polyamic acid (thatis prepared by diluting Semicofine SP-341 available from Toray Co., Ltd.with N-methyl-2-pyrrolidone). The substrate is heated under a nitrogengas flow subsequently at 150° C., at 250° C. and at 350° C.,respectively, for one hour, to form a lower pattern transfer filmconsisting of polyimide having a thickness of 500 nm. Aluminum isdeposited thereon to a thickness of 15 nm to form an upper patterntransfer film. The PAN-PEO-PAN triblock copolymer synthesized by thesimilar method to that in Example 47 is applied thereto in a thicknessof 80 nm spin-coated to form a pattern forming film. Thepolyacrylonitrile block has Mw of 144,600, the polyethylene oxide has Mwof 70,700, and Mw/Mn is 1.41. Then, a porous pattern forming film havinga structure having micro polymer phases is manufactured by the samemethod as in Example 47.

Reactive ion etching is performed to the sample under the conditions ofCF₄, 0.01 Torr, 150 W of progressive wave, and 30 W of reflected wave,to transfer the phase-separated pattern of the pattern forming film tothe upper pattern transfer film made of aluminum. Subsequently, reactiveion etching is performed to the sample under the conditions of O₂, 0.01Torr, 150 W of progressive wave, and 30 W of reflected wave, to removethe residue of the pattern forming film, and at the same time, to etchthe lower pattern transfer film formed of polyimide that are exposed tooutside through openings in the upper pattern transfer film. Further,reactive ion etching is performed under the conditions of CF₄, 0.01Torr, 150 W of progressive wave, and 30 W of reflected wave, to removethe upper pattern transfer film, and at the same time, to etch a part ofthe quartz substrate exposed through the openings formed in the patterntransfer film. Reactive ion etching is performed again under theconditions of O₂, 0.01 Torr, 150 W of progressive wave, and 30 W ofreflected wave, to remove the lower pattern transfer film. As a result,holes having a very high aspect ratio of a diameter of 110 nm and adepth of 1200 nm are formed over the entire surface of the quartzsubstrate at a density of 35/μm².

Example 52

A SiO₂ film having a thickness of 500 nm is formed on a silicon wafer. Asolution of polysilane represented by the following chemical formula(Mw=12,000, x=0.4) in toluene is applied to the SiO₂ film, followed bybaking, thereby manufacturing a polysilane pattern transfer film havinga thickness of 100 nm. To the polysilane transfer film, 0.5 wt % of3,5-di-tert-butyl-4-hydroxy toluene is added as an antioxidant.

The pattern transfer film consisting of polysilane is coated with adiblock copolymer consisting of polyacrylonitrile (Mw=12,000) andpolyethylene oxide (Mw=28,000) synthesized by the same method as that inExample 50, followed by baking at 90° C. for two minutes, to form apattern forming film having a thickness of 40 nm. The sample is placedin an oven, and heat-treated in a nitrogen atmosphere at 200° C. for 10minutes and then at 135° C. for 10 hours, and in air at 200° C. for 24hours, and further in a nitrogen atmosphere at 350° C. for 30 minutes.

The polysilane film is etched using the pattern forming film as a maskunder the conditions of HBr flow rate of 50 sccm, vacuum degree of 80mTorr and excitation power of 200 W. As a result, the pattern can betransferred to the polysilane film. Since the pattern forming film isleft remained on the polysilane film, it is found that the patternforming film has sufficient etch resistance. Then, the SiO₂ film isetched using the polysilane film pattern as a mask under the conditionsof C₄F₈ flow rate of 50 sccm, CO flow rate of 10 sccm, Ar flow rate of100 sccm, O₂ flow rate of 3 sccm, vacuum degree of 10 mTorr, andexcitation power of 200 W. The polysilane film has sufficient etchresistance, so that the pattern can be preferably transferred to theSiO₂ film. The remaining polysilane film can be easily removed using anaqueous organoalkali solution or a diluted hydrofluoric acid solution.

Incidentally, when the same procedures as described above are performedwithout addition of 3,5-di-tert-butyl-4-hydroxy toluene to thepolysilane transfer film, etching selectivity between the patternforming film and the polysilane pattern transfer film is reduced by 30%.

Example 53

A gold electrode is deposited on a glass substrate having a diameter of10 inches, a SiO₂ film having a thickness of 100 nm is formed thereon,and an aluminum film having a thickness of 50 nm is deposited thereon.

A diblock copolymer (polyacrylonitrile: Mw=127,700, polymethylene oxide:Mw=1,103,000; Mw/Mn=1.30) and polyacrylonitrile (Mw=45,000, Mw/Mn=1.37)are mixed at the weight ratio of 21:79. The mixture is dissolved inacetonitrile by 5 wt %, followed by filtering, to prepare a solution.The solution is applied to the quartz glass substrate by spin coatingand dried at 110° C. to form a pattern forming film having a thicknessof 970 nm.

The sample is placed in an oven and heat-treated in a nitrogenatmosphere at 210° C. for 10 minutes and then at 135° C. for 10 hours,and in air at 200° C. for 24 hours, and further in a nitrogen atmosphereat 350° C. for 30 minutes, to make the pattern-forming film porous.

The sample is subjected to wet etching with an aqueous solution ofhydrochloric acid and then by hydrofluoric acid, thereby transferringthe phase-separated pattern of the pattern forming layer to the aluminumlayer as well as to the SiO₂ layer. Thereafter, ashing is performed withan asher to remove the residue of pattern forming layer.

As a result, holes having a diameter of about 840 nm can be formed inthe aluminum layer and SiO₂ layer at a density of about 23,000 per unitarea of 300 μm×100 μm. The size distribution of holes is very uniformwithin the range of ±10%. This is because the block copolymer uniform inmolecular weight is used. Also, since the islands of block copolymer arepresent in the sea of the homopolymer, holes are formed at randompositions in some degree. Thus, if the sample is used as a porous gateelectrode of a field emission display (FED) of three-electrodestructure, it is expected that interference fringe due to regularity ofelectrodes can be prevented from occurring. Therefore, the method ofthis example can be suitably applied to the manufacture of porous gateelectrode of FED.

Example 54

Dioctyl phthalate as a plasticizer is added by 10 wt % to the mixture inExample 53 of the diblock copolymer and the polyacrylonitrilehomopolymer. The heat-treatment conditions for form microphaseseparation are set to as follows: under a nitrogen gas flow at 200° C.for 10 minutes and then at 135° C. for one hour, and in air at 200° C.for 24 hours, and further under a nitrogen gas flow at 350° C. for 30minutes. A film having micro polymer phases is formed in a similarmanner to that in Example 53 except for these conditions. Etching isperformed using the film having micro polymer phases. As a result, apattern of holes same as that in Example 53 can be formed in thesubstrate. As described above, addition of the plasticizer can shortenthe heat treatment time.

Example 55

Gold is sputtered on the surface of a copper plate. A 10% solution of adiblock copolymer (polymethylphenylsilane Mw=135,000, PMMA: Mw=61,000,Mw/Mn=1.10) in PGMEA is applied to the gold film, and then dried over 9days in a desiccator. The resultant film has a thickness of 0.2 mm. Thefilm is vacuum-dried for 3 days. An ultra-thin film is cut out from thisfilm, which is observed with a transmission electron microscope. As aresult, it is confirmed that formed is a three-dimensional bicontinuousstructure in which both the polysilane phase and the PMMA phase areformed continuously.

The sample is irradiated with an electron beam at an exposure dose of150 kGy, and the is heat-treated in air at 150° C. for 2 hours and at200° C. for 12 hours, and further under an argon gas flow at 500° C. forone hour. When the film is observed with a transmission electronmicroscope (TEM), it is observed that the PMMA phase is eliminated andthe polysilane phase forms a continuous structure in the form of asponge. The structure is almost same as the original three-dimensionalbicontinuous structure, in which continuous pores of the order ofnanometers are formed regularly.

Copper electroplating is performed using the copper plate on which theporous film is formed as a working electrode, another copper plate as acounter electrode, and a saturated calomel electrode as a referenceelectrode. A saturated aqueous solution of copper sulfate is employed asan electrolyte solution, and electrolysis voltage is set to −0.1V vsSCE. As a result, a nanocomposite film having a porous film in whichpores are filled with copper is manufactured.

Example 56

Synthesis of a polysilane-polyethylene oxide Diblock Copolymer:

As monomers, a masked disilene and ethylene oxide are employed. As apolymerization initiator, sec-butyl lithium is employed. These monomersare successively introduced into THF at a reaction temperature of −78°C., and thus a diblock copolymer comprising a polybutylmethylsilanechain and a polyethylene oxide chain is synthesized by living anionpolymerization. The diblock copolymer has Mw of 70,500 and Mw/Mn of 1.2,the polysilane unit has Mw of 14,500, and the polyethylene oxide unithas Mw of 56,000.

A quartz substrate is spin-coated with a solution of polyamic acid (thatis prepared by diluting Semicofine SP-341 available form Toray Co., Ltd.with N-methyl-2-pyrrolidone). The substrate is heated under a nitrogengas flow at 150° C., at 250° C. and at 350° C., respectively, for onehour, to form a polyimide film (a pattern transfer film). The polyimidefilm is coated with a solution of the diblock copolymer synthesized asdescribed above to form a pattern forming film. The pattern forming filmis irradiated with an ultraviolet ray from a high-pressure mercury lampto photo-oxidize the polysilane chain. The sample is heat-treated in airat 150° C. for one hour, and in a nitrogen atmosphere at 200° C. for 2hours, at 250° C. for 2 hours, and at 350° C. for 30 minutes to make thefilm porous. Reactive ion etching is performed using the porous film asa mask under the conditions of O₂, 0.01 Torr, 150 W of progressive wave,and 30 W of reflected wave. At this time, the photo-oxidized polysilanefilm has sufficient etch resistance, making it possible to transfer apreferable pattern to the polyimide film. Further, the substrate isetched using the polyimide film as a mask. As a result, holes having adiameter of 14 nm and a depth of 10 nm are formed over the entiresurface of the substrate at a density of about 2400/μm² and atapproximately equal intervals.

Example 57

The same diblock copolymer as employed in Example 43 is dissolved by 1wt % in methylene chloride. To the solution, 1 wt % oftetrabutylammonium hexachloro-platinate (IV) based on the weight of thepolymer is added. The solution is cast on a SiO substrate to form apattern forming film having a thickness of 20 nm. The sample is heatedat 110° C. for 90 seconds to evaporate the solvent. Thereafter, thesample is placed in an oven and is heat-treated in a nitrogen atmosphereat 150° C. for 5, at 200° C. for 5 hours, at 300° C. for 5 hours and at350° C. for 30 minutes.

Reactive ion etching is performed to the sample under the conditions ofCF₄, 0.01 Torr, 150 W of progressive wave, and 30 W of reflected wave toetch the SiO substrate. As a result, holes having a diameter of 12 nmand a depth of 25 nm are formed over the entire surface of the SiOsubstrate at a density of about 2000/μm² and at approximately equalintervals. Further, platinum particles are deposited in the holes. Byallowing a magnetic material to grow using the deposited platinumparticles as nuclei, a magnetic recording medium of hard disk can bemanufactured.

Example 58

Synthesis of Graft Copolymer:

Styrene-terminated polyethylene oxide macromer (a) (Mw=14,100,Mw/Mn=1.04) and polysilsesquioxane derivative monomer (b) (where R is ahexyl group), represented by the following chemical formulas,respectively, are dissolved in THF, to which AIBN as a radical initiatoris added, and then the mixture is heated in an argon atmosphere at 60°C. for 60 hours to synthesize a graft copolymer by radicalpolymerization. The graft copolymer has Mw of 101,000 and Mw/Mn of 2.1,the polysilsesquioxane derivative unit has Mw of 16,400, and thepolyethylene oxide macromer unit has Mw of 84,600.

The graft copolymer is dissolved by 2 wt % in ethyl lactate, which isapplied to a substrate and the naturally dried to form a pattern formingfilm. The sample is heated at 110° C. for 90 seconds to evaporate thesolvent. The sample is heat-treated at 200° C. for one hour and at 350°C. for 5 hours to make the pattern forming film porous. Reactive ionetching is performed to the sample under the conditions of CF₄, 0.01Torr, 150 W of progressive wave, and 30 W of reflected wave to etch thesubstrate. As a result, many projections having a diameter of 18 nm anda height of 10 nm are formed on the substrate.

Example 59

A 10% solution of a diblock copolymer (polyacrylonitrile Mw=137,000,polypropylene oxide Mw=32,000, Mw/Mn=1.45) in PGMEA is poured into aTeflon Petri dish, and then dried in a desiccator under an argon gasflow over 9 days. The thickness of the formed film is 0.2 mm. The filmis vacuum-dried for 3 days. An ultra-thin film is cut out from the film,which is observed with a transmission electron microscope. As a result,it is confirmed that formed is a cylindrical structure in whichcylindrical polypropylene oxide phases are formed in the matrix of thepolyacrylonitrile phase.

The sample is irradiated with an electron beam at an exposure dose of 20kGy. The sample is heat-treated in air at 150° C. for 2 hours and at200° C. for 12 hours, and under an argon gas flow at 500° C. for onehour and at 1200° C. for one hour. When the sample is observed with TEM,it is found that formed is porous carbon in the form of a honeycombretaining the cylindrical structure having pores with a diameter ofabout 20 nm. The porous carbon can be preferably employed as a carbonelectrode.

When porous carbon is manufactured in the same manner as described aboveexcept that polyacrylonitrile-propylene oxide diblock copolymer(polyacrylonitrile Mw=69,000, polypropylene oxide Mw=14,000, Mw/Mn=1.42)is employed as a diblock copolymer. In this case, the porous carbon haspores with a diameter of about 9 nm.

Example 60

A 10% solution of a diblock copolymer (polyacrylonitrile Mw=137,000,polypropylene oxide Mw=62,000, Mw/Mn=1.45) in PGMEA is poured into aTeflon Petri dish, and then dried in a desiccator under an argon gasflow over 9 days. The thickness of the formed film is 10 μm. The film isvacuum-dried for 3 days. An ultra-thin film is cut out from the film,which is observed with a transmission electron microscope. As a result,it is confirmed the formed is a three-dimensional bicontinuous structurein which both the polyacrylonitrile phase and the polypropylene oxidephase are formed continuously.

The sample is irradiated with an electron beam at an exposure dose of 20kGy. The film is heat-treated in air at 150° C. for 2 hours and at 200°C. for 12 hours, and under an argon gas flow at 500° C. for one hour andat 1200° C. for one hour. TEM observation shows that porous carbonretaining a bicontinuous structure is formed. The porous carbon can bepreferably employed as a carbon electrode.

Example 61

A 10% solution of a diblock copolymer A (polyacrylonitrile Mw=68,000,polypropylene oxide Mw=32,000, Mw/Mn=1.45) is poured into a Teflon Petridish, and then is dried over 9 days in a desiccator to manufacture afilm. Platinate chloride and ruthenium chloride (Pt/Ru=1:1) are added tothe solution of the diblock copolymer A. Likewise, a 10% solution of adiblock copolymer B (polyacrylonitrile Mw=137,000, polypropylene oxideMw=62,000, Mw/Mn=1.45) is poured into a Teflon Petri dish, and then isdried over 9 days in a desiccator to manufacture a film. These filmsthus manufactured have a thickness of 10 μm, respectively. The films arevacuum-dried for 3 days. Ultra-thin films are cut out from these films,respectively, which are observed with a transmission electronmicroscope. As a result, it is confirmed that these films has astructure having micro polymer phases in which a polyacrylonitrile phaseand a polypropylene oxide phase are entangled with each other. Thediblock copolymer A is treated with formalin to generate Pt particlesand Ru particles.

A solution of polyamic acid (that is prepared by diluting SemicofineSP-341 available from Toray Co., Ltd. with N-methyl-2-pyrrolidone) isapplied to a silicon wafer with an applicator, immediately after thatwafer is placed in a large amount of pure water so as not to evaporatethe solvent and is immersed in water for 5 hours. The film isvacuum-dried at 50° C. for 8 hours, and further vacuum-dried at 170° C.for 8 hours. Next, the film is heat-treated in a nitrogen gas atmosphereat 200° C., at 250° C., at 300° C. and at 350° C., respectively, for onehour, to provide a three-dimensional porous polyimide film having anaverage pore size of about 0.5 μm.

The diblock copolymer A film, the diblock copolymer B film and theporous polyimide film are laminated and pressed to each other. Thelaminate is heat-treated in air at 150° C. for 2 hours and at 200° C.for 12 hours, and further under an argon gas flow at 500° C. for onehour and at 1200° C. for one hour. TEM observation of the cross-sectionof the sample shows that three-layered porous carbon laminate eachhaving a pore size of about 20 nm, 40 nm and 0.1 to 0.5 μm,respectively.

On the other hand, to the diblock copolymer B (polyacrylonitrileMw=137,000, polypropylene oxide Mw=62,000, Mw/Mn=1.45), a colloidalsolution containing Pt fine particles having an average particle size of5 nm that are generated using the diblock copolymer B as a coagulationinhibitor is added, and then a cast film having a thickness of 10 μm isformed. Pt fine particles are segregated at the interface of thestructure having micro polymer phases of the diblock copolymer B. Thecast film is heat-treated in air at 150° C. for 2 hours and at 200° C.for 12 hours, and further under an argon gas flow at 500° C. for onehour and at 1200° C. for one hour to manufacture a Pt-dispersed porouscarbon film.

An electrolyte film consisting of Naphyon 117 (DuPont Co., Ltd.) havinga thickness of 50 μm is formed on the porous layer having the pore sizeof 20 nm among the three layers of the porous carbon laminate filmemployed as a methanol fuel electrode, and then the Pt-dispersed porouscarbon film as an air electrode is laminated thereon, therebymanufacturing a thin direct methanol fuel cell having a thickness of assmall as 0.1 μm. When methanol and air are supplied to the cell so as toactuate the cell at 60° C., a continuous power generation is confirmed.

Example 62

3.5 g of polyoxyethylene (23) lauryl ether (Wako Junyaku Kogyo Co.,Ltd.) as a surfactant, 0.2 g of glycerin, 3.4 g of furfuryl alcohol as aprecursor of a thermosetting resin and 1.1 g of hydrochloric acid aredissolved in 29 g of water. To the aqueous solution, 33 g of isooctaneis added and vigorously stirred and then the mixture is reacted at 60°C. for one month. The reaction mixture is filtered and the precipitateis separated out and washed with water and dried in vacuum to provide1.0 g of black carbon precursor powder. The powder is fired in air at200° C. for 2 hours and subsequently under a nitrogen gas flow at 500°C. for one hour to provide 0.4 g of carbon structure.

FIGS. 11 and 12 show SEM photographs of the carbon structures. As shownin FIGS. 11 and 12, the carbon structures have a complex structure thatis spherical as a whole and has circular structures on the surfacethereof.

When the reaction and firing are performed in the same manner asdescribed above except that 0.2 g of a 20 wt % solution of titaniumtrichloride in hydrochloric acid is added to the above aqueous solution.In this case, 0.8 g of the carbon structure is obtained. In such amanner, addition of titanium trichloride can improve the yield.

Example 63

Synthesis of Diblock Copolymer:

A diblock polymer consisting of 1,2-polybutadiene chain and polyethyleneoxide chain is synthesized by living anion polymerization. The1,2-polybutadiene chain has Mw of 65,000, the polyethylene oxide chainhas Mw of 13,200, and Mw/Mn is 1.1.

Pattern Formation:

A 2 wt % solution of a mixture prepared by adding 3 wt % of3,3′,4,4′-tetrakis(t-butylperoxycarbonyl) benzophenone to the resultantdiblock polymer is filtered. The solution is applied to a 3-inch quartzglass substrate by spin coating at a rate of 2,500 rpm to form a patternforming film. The sample is placed in an oven and is heat-treated in anitrogen atmosphere at 135° C. for 2 hours and at 170° C. for one hour.The heat-treatment at 170° C. allows the 1,2-polybutadiene chain to bethree-dimensionally cross-linked. Further, the sample is heat-treated ina nitrogen atmosphere at 170° C. for 30 minutes. When the surface of thesubstrate after the heat treatments is observed with AFM, it is foundthat holes having a size of about 13 nm are formed over the entiresurface of the pattern forming film.

Reactive ion etching is performed to the sample under the conditions ofCF₄, 0.01 Torr, 150 W of progressive wave, and 30 W of reflected wave.Thereafter, Reactive ion etching is performed to the sample under theconditions of O₂, 0.01 Torr, 150 W of progressive wave, and 30 W ofreflected wave to remove the residue of the pattern forming film.

As a result, holes having a diameter of 13 nm and a depth of 15 nm areformed over the entire surface of quartz glass substrate at a density ofabout 2000/μm² and at approximately equal intervals. A CoPtCr thin filmhaving a thickness of 15 nm is deposited on the quartz substrate bysputtering. Carbon having a thickness of 10 nm is deposited as aprotective film on the CoPtCr thin film by sputtering, from whichanomalous projections are removed by tape vanishing, and then alubricant is applied thereto to manufacture a high-density magneticrecording medium. The medium has perpendicular magnetic anisotropy of1.8 kOe.

Example 64

Pattern Formation:

A 2 wt % solution of a mixture that is prepared by adding 3 wt % of3,3′,4,4′-tetrakis(t-butylperoxy-carbonyl)benzophenone is added to thesame diblock polymer as that employed in Example 63 is filtered. Thesolution is applied to a 3-inch quartz glass substrate by spin coatingat a rate of 2,500 rpm to form a pattern forming film. The sample isplaced in an oven and is heat-treated in a nitrogen atmosphere at 135°C. for 2 hours and at 170° C. for one hour. The heat-treatment at 170°C. allows the polybutadiene chain to be three-dimensionallycross-linked. Further, the sample is heat-treated in a nitrogenatmosphere at 170° C. for 30 minutes. When the surface of the substrateafter the heat treatments is observed with AFM, it is found that holeshaving a size of about 13 nm are formed over the entire surface of thepattern forming film.

Reactive ion etching is performed to the sample under the conditions ofCF₄, 0.01 Torr, 150 W of progressive wave, and 30 W of reflected wave.After etching, the substrate is further treated with hydrofluoric acid.The sample is immersed in a solution of tin (II) chloride (0.1 mL/L of37% concentrated sulfuric acid is added to 1.0 g/L of SnCl₂) for 20seconds, and then the sample is washed with pure water. Subsequently,the sample is immersed in a solution of palladium chloride (0.1 mL/L of37% concentrated sulfuric acid is added to 0.1 g/L of PdCl₂) for 20seconds, and then the sample is washed with pure water. These operationsto immerse the sample into the solutions of tin (II) chloride andpalladium chloride are repeated several times.

As a result, provided is a structure in which palladium dots having adiameter of about 10 nm are formed over the entire surface of the quartzglass substrate at a density of about 2000/μm² and at approximatelyequal intervals. A CoPtCr thin film having a thickness of 15 nm isdeposited on the quartz substrate by sputtering. Carbon having athickness of 10 nm is deposited as a protective film on the CoPtCr thinfilm by sputtering, from which anomalous projections are removed by tapevanishing, and then a lubricant is applied thereto to manufacture ahigh-density magnetic recording medium.

The above dot-like palladium can also be used as a mask or as a dottedelectrode.

Example 65

Polyethylene oxide whose ends are treated with 3,5-diaminobenzoate(weight-average molecular weight Mw=20,000) is reacted withparaphenylenediamine and pyromellitic anhydride to synthesize polyamicacid having polyethylene oxide chains as graft chains. The weight ratiobetween the polyamic acid moiety and the polyethylene oxide moiety isset to 1:2. One part by weight of bis(4-maleimidophenyl)methane is addedto 30 parts by weight of the synthesized polyamic acid, and then asolution in N-methylpyrrolidone is prepared. The solution is applied toa glass plate using an applicator to form a sheet having a thickness of10 μm. The sheet is subjected to heat-treatment in a nitrogen flow at150° C., 250° C. and 350° C. for one hour, respectively, to provide aporous sheet. The resultant porous sheet has a porous structure to whichtransferred is a bicontinuous phase-separated structure consisting ofpolybutadiene cylinder phases highly branched in a three-dimensionalnetwork configuration.

The resultant polyimide porous sheet is subjected to repeating processescomprising steps of being impregnated with apoly(2-bromoethyl)silsesquioxane, being irradiated with an ultravioletray, and being heat-treated at 80° C., by five times, and thuspoly(2-bromoethyl)silsesquioxane is sufficiently loaded into pores ofthe porous sheet. The porous sheet is subjected to oxygen ashing underthe conditions of 800 W and 1 Torr. As a result, it is possible tomanufacture a silica porous body having a nanostructure that istransferred using the porous structure of the polyimide porous sheet asa template.

A mixed solution of acrylonitrile mixed with 10 wt % of3,3′,4,4′-tetra(t-butylperoxycarbonyl) benzophenone is prepared. Thesilica porous body is impregnated with the solution. The silica porousbody is irradiated with an ultraviolet ray, thereby polymerizing andcuring the acrylonitrile. The structure is heated in air at 210° C. for24 hours, and then heated in a nitrogen flow from 210° C. to 800° C. ata rate of temperature rise of 10° C. per minute so as to be carbonized.The composite of silica and carbon is treated with hydrofluoric acid tosolve out the silica. As a result, it is possible to manufacture porouscarbon having continuous pores reflecting the morphology of thepolyimide porous sheet.

Example 66

A block copolymer of PS having a molecular weight of 65,000 and PMMAhaving a molecular weight of 13,000, and platinum particles covered withPMMA are prepared. One wt % of the platinum particle-including PMMA isadded to the block copolymer. The resultant mixture is dissolved inethyl cellosolve acetate to prepare a 10 wt % solution.

A SiO substrate having a diameter of 3 inches is spin-coated with thesolution at a rate of 2,500 rpm. The substrate is heated at 110° C. for90 seconds to evaporate the solvent. The substrate is placed in an ovenand the is annealed in a nitrogen atmosphere at 210° C. for 10 minutes,subsequently at 135° C. for 10 hours. When the SiO substrate is observedwith an atomic force microscope in a phase mode, it is confirmed thatislands of PMMA having a diameter of about 17 nm are formed in the seaof PS.

RIE is performed to the sample under the conditions of CF₄, 0.01 Torr,150 W of progressive wave, and 30 W of reflected wave to etch the PMMAselectively, and further to etch the exposed underlayer using theremaining PS pattern as a mask. Ashing is performed to the sample underthe conditions of O₂, 0.01 Torr, 150 W of progressive wave, and 30 W ofreflected wave to remove the mask made of PS.

It is observed with SEM and AFM that holes having a diameter of about 20nm are formed over the entire surface of the 3-inch SiO substrate atapproximately equal intervals. Also, it is observed that the platinumparticles are aggregated at the center of the holes.

Example 67

A block copolymer of polystyrene having a molecular weight of 26,000 andpoly(2-vinylpyridine) having a molecular weight of 5,600, platinumparticles covered with poly(2-vinylpyridine), and platinum particlescovered with polymethyl acrylate are prepared. The two kinds of platinumparticle-including polymers are added by 1 wt %, respectively, to theblock copolymer. The resultant mixture is dissolved in diglyme toprepare a 10% solution.

A SiO substrate having a diameter of 3 inches is spin-coated with thesolution at a rate of 2,500 rpm. The substrate is heated at 110° C. for90 seconds to evaporate the solvent. The substrate is placed in an ovenand is annealed in a nitrogen atmosphere at 210° C. for 10 minutes,subsequently at 135° C. for 10 hours.

Ashing is performed to the entire surface of the sample under theconditions of O₂, 0.01 Torr, 150 W of progressive wave, and 30 W ofreflected wave to remove the block copolymer. As a result, only platinumparticles remain on the substrate.

It is observed with SEM and AFM that platinum particles having aparticle size of about 4 nm are dispersed with forming a trianglelattice of about 25 nm over the entire surface of the substrate.

After the surface of the substrate is lightly sputter-etched at 100 Wfor one minute, CoPt is sputtered under a pressure of 2 Pa, therebydepositing a magnetic layer having a thickness of 20 nm with using theplatinum particles as seeds. The result of determination of the coerciveforce from the hysteresis curve shows 13 kOe.

For the purpose of comparison, a magnetic layer is deposited on a glasssubstrate on which metal fine particles are dispersed. The magneticlayer has coercive force of 5 kOe.

Example 68

In place of platinum particles covered with poly(2-vinylpyridine)employed in Example 67, platinum particles covered with a blockcopolymer comprising PS having a molecular weight of 4,800 andpoly(2-vinylpyridine) having a molecular weight of 4,300 are employed.One wt % of the platinum particle-including block copolymer is added tothe block copolymer employed in Example 67. The resultant mixture isdissolved in ethyl cellosolve acetate to prepare a 10-wt % solution.

A SiO substrate having a diameter of 3 inches is spin-coated with thesolution at a rate of 2,500 rpm. The substrate is heated at 110° C. for90 seconds to evaporate the solvent. The substrate is placed in an ovenand is annealed in a nitrogen atmosphere at 210° C. for 4 hours,subsequently at 135° C. for 10 hours.

When the substrate is observed with an atomic force microscope in aphase mode, it is confirmed that islands of poly(2-vinylpyridine) havinga size of about 17 nm are dispersed in the sea of PS in which metal fineparticles locally exist at the interface between the islands and thesea.

RIE is performed to the sample under the conditions of CF₄, 0.01 Torr,150 W of progressive wave, and 30 W of reflected wave to etch thepoly(2-vinylpyridine) selectively, and further to etch the exposedunderlayer using the remaining PS pattern as a mask. Ashing is performedto the sample under the conditions of O₂, 0.01 Torr, 150 W ofprogressive wave, and 30 W of reflected wave to remove the mask made ofPS.

It is observed with SEM and AFM that holes having a diameter of about 20nm are formed over the entire surface of the 3-inch SiO substrate atapproximately equal intervals. Also, it is observed that the platinumparticles are segregated at the edges of the holes.

Example 69

Another method for manufacturing the field emission display (FED) deviceshown in FIG. 9 will be described. Similar to the method in Example 27,the cathode conductor 102 is formed on the insulative substrate 101, andthen a portion of the cathode conductor 102 is etched. The resistancelayer 103 formed to cover the cathode conductor 102, and then theresistance layer 103 is patterned to form a plurality of terminals 103A.The insulating layer 104 is formed to cover the cathode conductor 102and the resistance layer 103, and then the gate conductor 105 is formedon the insulating layer 104.

Then, a resist is patterned to protect intersecting portions betweengate wires and emitter wires. A solution of a mixture of the PS-PMMAdiblock copolymer used in Example 66 and platinum particles coated withPMMA is applied to the gate conductor 105 by spin coating and thendried, followed by annealing, thereby forming a film having micropolymer phases. RIE with CF₄ gas is performed to the film having micropolymer phases, thus the PMMA in the film having micro polymer phases isselectively etched, and further the gate conductor 105 is etched withusing the pattern of remaining PS as mask, thereby transferring thepattern to the gate conductor 105. Thereafter, ashing is performed withan O₂ asher, thereby removing the remaining organic substances. In sucha manner, many openings 106 having a diameter of about 840 nm are formedin the gate conductor 105. Wet etching with a buffered hydrofluoric acid(BHF) or RIE with a gas such as CHF₃ is performed to remove theinsulating layer 104 in the openings 106 until the resistance layer 103is exposed to the outside. As a result, it is confirmed that platinumparticles are deposited on the bottom of the openings 106.

Then, aluminum is obliquely deposited by electron beam (EB) evaporationto form a peeling layer. Molybdenum is normally deposited on the peelinglayer in the perpendicular direction by EB evaporation, therebydepositing molybdenum in a conical configuration inside the openings 106to form the emitters 107. Thereafter, the peeling layer is removed witha peeling solution such as phosphoric acid, thereby manufacturing an FEDdevice.

Example 70

A block copolymer comprising poly(2-vinylpyridine) having a molecularweight of 83,000 and poly(methyl acrylate) having a molecular weight of78,000, platinum particles coated with poly(2-vinylpyridine) andplatinum particles coated with polymethyl acrylate are prepared. Then, 1wt % of each of the polymer-coated platinum particles is added to theblock copolymer. The mixture is dissolved in THF to prepare a 10-wt %solution. The solution is placed in a Teflon Petri dish to allow thesolvent to evaporate over 10 days. Further, drying is performed invacuum at 60° C. over 3 days, and thus a first film having a thicknessof 0.2 mm is provided.

Poly(2-vinylpyridine) having a molecular weight of 143,000 and platinumparticles covered with poly(2-vinylpyridine) are prepared. Then, 1 wt %of the polymer-coated platinum particles is added to the homopolymer.The mixture is dissolved in THF to prepare a 10-wt % solution. Thesolution is placed in a Teflon Petri dish to allow the solvent toevaporate over 10 days. Further, drying is performed in vacuum at 60° C.for 3 days, thus a second film having a thickness of 0.05 mm isprovided.

Polymethyl acrylate having a molecular weight of 160,000 and platinumparticles covered with polymethyl acrylate are prepared. Then, 1 wt % ofthe polymer-coated platinum particles is added to the homopolymer. Themixture is dissolved in THF to prepare a 10-wt % solution. The solutionis placed in a Teflon Petri dish to allow the solvent to evaporate over10 days. Further, drying is performed in vacuum at 60° C. for 3 days,thus a third film having a thickness of 0.05 mm is provided.

The second film, the first film and the third film are laminated in thisorder and annealed in a nitrogen atmosphere at 160° C. for 40 hours.Observation with TEM shows that a lamella structure is formed in thefirst film. Further, these films are annealed at 240° C. for 10 hours.Observation again with TEM shows that the polymer is fired and platinumis made into a continuous product. Aluminum is deposited on both sidesof the structure to form electrodes. The structure is then cut into 1cm×1 cm to manufacture a capacitor.

Example 71

A block copolymer comprising polystyrene (molecular weight: 35,000) andpolyethylene oxide (molecular weight: 70,000), and platinum particlescovered with the block copolymer are prepared. Then, 1 wt % of thepolymer-coated platinum particles is added to the block copolymer. Themixture is dissolved in THF to prepare a 10% solution. The solution isplaced in a Teflon Petri dish to allow the solvent to evaporate over 10days. Further, drying is performed in vacuum at 60° C. for 3 days toprovide a film having a thickness of 0.05 mm. The film is annealed in anitrogen atmosphere at 140° C. for 40 hours. TEM observation shows thata cylindrical structure is formed in the film. Further, the film isannealed at 240° C. for 10 hours. When the film is observed by TEMagain, many pores 62 are formed in the polymer 61 as shown in FIG. 13,and many platinum particles 63 are adhered on the wall facing the pores62. The film is employed as a cathode catalytic layer of a fuel cell.

A block copolymer comprising polystyrene (molecular weight: 35,000) andpolyethylene oxide (molecular weight: 70,000), and platinum particlescovered with this block copolymer coating are prepared. Then, 1 wt % ofthe polymer-coated ruthenium particles is added to the block copolymer.The mixture is dissolved in THF to prepare a 10-wt % solution. Thesolution is placed in a Teflon Petri dish to allow the solvent toevaporate over 10 days. Further, drying in vacuum at 60° C. over 3 daysprovides a film having a thickness of 0.05 mm. The film is annealed in anitrogen atmosphere at 140° C. for 40 hours. Observation with TEM showsthat a cylindrical structure appears in the film. The film is annealedfor 10 hours at 240° C. Observation again with TEM shows that a largenumber of pores are formed and a large number of ruthenium fineparticles are adhered on the walls facing the pores, as shown in FIG.13. The thin film is employed as a cathode catalytic layer of fuel cell.

A direct methanol fuel cell shown in FIG. 7 is manufactured.

FIG. 7 shows a conceptual diagram of a direct methanol fuel cell. Theanode catalytic layer 11 and the cathode catalytic layer 14 sandwichesthe electrolyte film 16 made of a proton conductor. On the side of theanode catalytic layer 11, the fuel-evaporating layer 12 and thefuel-permeating layer 13 are provided. On the side of the cathodecatalytic layer 14, the water-holding gas channel 14 is provided.

For the purpose of comparison, using a cathode catalytic layer having astructure that a platinum catalyst is buried in the matrix of a film anda cathode catalytic layer having a structure that a ruthenium catalystis buried in the matrix of a film, a direct methanol fuel cell shown inFIG. 7 is manufactured.

The fuel cell of the present invention has higher power generationefficiency by at least twice as compared with the fuel cell of thecomparative example.

1. A method for manufacturing a porous structure, comprising: forming amolded product consisting of a pattern forming material comprising acopolymer selected from the group consisting of a block copolymer and agraft copolymer; the block copolymer and the graft copolymer eachhaving: a first polymer chain whose main chain may be cut by irradiationwith an energy beam selected from the group consisting of an electronbeam, a γ-ray beam, and an X-ray beam, and a second polymer chain whichdoes not decompose upon irradiation with the energy beam; forming amicrophase-separated structure in the molded product; the structurecomprising: an energy-beam-decomposable polymer phase comprising thefirst polymer, and a remaining polymer phase comprising the secondpolymer; cutting the main chain of the first polymer in themicrophase-separated structure by irradiating the molded product withthe energy beam; and forming a porous structure comprised of theremaining polymer phase by etching and selectively removing theenergy-beam-decomposable polymer phase; wherein the copolymer is madeself-supporting prior to the etching and selectively removing theenergy-beam-decomposable polymer phase.
 2. The method according to claim1, wherein the polymer chain whose main chain is cut by irradiation withan energy beam is a polyalkylmethacrylate chain.
 3. The method accordingto claim 1, wherein the polymer chain whose main chain is cut byirradiation with an energy beam has a molecular weight of 100,000 orless, and wherein the copolymer has a molecular weight distribution(Mw/Mn) of 1.20 or less, and wherein the molecular weight ratio betweenthe indecomposable polymer chain and the decomposable polymer chain isranging from 75:25 to 90:10.
 4. The method according to claim 1, whereinthe copolymer has a molecular weight of 50,000 or more and has amolecular weight distribution (Mw/Mn) of 1.15 or less, and wherein amolecular weight ratio between the indecomposable polymer chain and thedecomposable polymer chain is ranging from 75:25 to 90:10.
 5. The methodaccording to claim 1, further comprising using the porous structure asat least part of a separator of an electrochemical cell comprising apair of electrodes and a separator interposed between the electrodes andimpregnated with an electrolyte.
 6. The method according to clam 5,wherein the porous structure has an aggregated structure of domains, thedomains having a radius of gyration of 50 μm or less in which unit cellshaving a radius of gyration from 10 to 500 nm are periodically arranged.7. The method according to claim 1, further comprising using the porousstructure as a hollow fiber filter.
 8. The method according to claim 7,wherein the porous structure has an aggregated structure of domains, thedomains having a radius of gyration of 50 μm or less in which unit cellshaving a radius of gyration from 10 to 500 nm are periodically arranged.9. The method according to clam 1, wherein the porous structure has anaggregated structure of domains, the domains having a radius of gyrationof 50 μm or less in which unit cells having a radius of gyration from 10to 500 nm are periodically arranged.
 10. The method of claim 1, whereinthe molded product is formed by at least one of hot press molding,injection molding and transfer molding.
 11. The method of claim 1,wherein the molded product is formed by melting and molding thecopolymer in the absence of a substrate.
 12. The method of claim 1,further comprising: filling the pores of the porous structure with aninorganic substance.
 13. The method of claim 12, wherein the inorganicsubstance is filled by at least one of plating or chemical vapordeposition.
 14. The method of claim 1, wherein the molded product is afiber formed by extrusion molding the copolymer.